{"id":105242,"date":"2026-09-15T05:56:22","date_gmt":"2026-09-14T21:56:22","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/105242.html"},"modified":"2026-09-15T05:56:22","modified_gmt":"2026-09-14T21:56:22","slug":"%e3%80%90rust%e5%85%a5%e9%97%a8%e7%9f%a5%e8%af%86%e7%82%b9%e5%ad%a6%e4%b8%8e%e7%bb%83%e3%80%91%e7%ac%ac29%e8%af%be%ef%bc%9a%e6%99%ba%e8%83%bd%e6%8c%87%e9%92%88%e8%bf%9b%e9%98%b6%e4%b8%8e%e5%86%85","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/105242.html","title":{"rendered":"\u3010Rust\u5165\u95e8\u77e5\u8bc6\u70b9\u5b66\u4e0e\u7ec3\u3011\u7b2c29\u8bfe\uff1a\u667a\u80fd\u6307\u9488\u8fdb\u9636\u4e0e\u5185\u90e8\u53ef\u53d8\u6027"},"content":{"rendered":"

\u77e5\u8bc6\u70b9：Box \u56de\u987e \u2014 \u5806\u4e0a\u5206\u914d<\/h2>\n

\/\/ Box<T> \u628a\u6570\u636e\u653e\u5728\u5806\u4e0a，\u6808\u4e0a\u53ea\u5b58\u6307\u9488<\/span>
\n\/\/ \u9002\u7528\u573a\u666f：<\/span>
\n\/\/ 1. \u7f16\u8bd1\u65f6\u5927\u5c0f\u672a\u77e5\u7684\u7c7b\u578b（\u5982\u9012\u5f52\u7c7b\u578b）<\/span>
\n\/\/ 2. \u5927\u91cf\u6570\u636e\u9700\u8981\u8f6c\u79fb\u6240\u6709\u6743\u4f46\u4e0d\u60f3\u62f7\u8d1d<\/span>
\n\/\/ 3. \u53ea\u5173\u5fc3\u503c\u662f\u5426\u5b9e\u73b0\u4e86\u67d0\u4e2a trait（trait \u5bf9\u8c61）<\/span><\/p>\n

\/\/ \u9012\u5f52\u7c7b\u578b\u5fc5\u987b\u7528 Box<\/span>
\n#[derive(Debug)]<\/span>
\nenum<\/span> List<\/span> {<\/span>
\n Cons<\/span>(<\/span>i32<\/span>,<\/span> Box<\/span><<\/span>List<\/span>><\/span>)<\/span>,<\/span> \/\/ Box \u8ba9\u7f16\u8bd1\u5668\u77e5\u9053\u5927\u5c0f<\/span>
\n Nil<\/span>,<\/span>
\n}<\/span><\/p>\n

fn<\/span> build_list<\/span>(<\/span>)<\/span> -><\/span> List<\/span> {<\/span>
\n List<\/span>::<\/span>Cons<\/span>(<\/span>1<\/span>,<\/span> Box<\/span>::<\/span>new<\/span>(<\/span>
\n List<\/span>::<\/span>Cons<\/span>(<\/span>2<\/span>,<\/span> Box<\/span>::<\/span>new<\/span>(<\/span>
\n List<\/span>::<\/span>Cons<\/span>(<\/span>3<\/span>,<\/span> Box<\/span>::<\/span>new<\/span>(<\/span>
\n List<\/span>::<\/span>Nil<\/span>
\n )<\/span>)<\/span>
\n )<\/span>)<\/span>
\n )<\/span>)<\/span>
\n}<\/span><\/p>\n

fn<\/span> print_list<\/span>(<\/span>list:<\/span> &<\/span>List<\/span>)<\/span> {<\/span>
\n match<\/span> list {<\/span>
\n List<\/span>::<\/span>Cons<\/span>(<\/span>val,<\/span> next)<\/span> =><\/span> {<\/span>
\n print!<\/span>(<\/span>"{} "<\/span>,<\/span> val)<\/span>;<\/span>
\n print_list<\/span>(<\/span>next)<\/span>;<\/span>
\n }<\/span>
\n List<\/span>::<\/span>Nil<\/span> =><\/span> println!<\/span>(<\/span>"Nil"<\/span>)<\/span>,<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

\/\/ Box \u5b9e\u73b0 Deref，\u53ef\u4ee5\u50cf\u666e\u901a\u5f15\u7528\u4e00\u6837\u4f7f\u7528<\/span>
\nfn<\/span> deref_example<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> b =<\/span> Box<\/span>::<\/span>new<\/span>(<\/span>5<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u503c: {}"<\/span>,<\/span> *<\/span>b)<\/span>;<\/span> \/\/ \u81ea\u52a8\u89e3\u5f15\u7528<\/span>
\n println!<\/span>(<\/span>"\u503c: {}"<\/span>,<\/span> b)<\/span>;<\/span> \/\/ Display \u4e5f\u4f1a\u81ea\u52a8\u89e3\u5f15\u7528<\/span>
\n}<\/span><\/p>\n

\/\/ Box \u5b9e\u73b0 Drop，\u79bb\u5f00\u4f5c\u7528\u57df\u81ea\u52a8\u91ca\u653e\u5806\u5185\u5b58<\/span>
\nfn<\/span> drop_example<\/span>(<\/span>)<\/span> {<\/span>
\n {<\/span>
\n let<\/span> b =<\/span> Box<\/span>::<\/span>new<\/span>(<\/span>String<\/span>::<\/span>from<\/span>(<\/span>"hello"<\/span>)<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"{}"<\/span>,<\/span> b)<\/span>;<\/span>
\n }<\/span> \/\/ b \u79bb\u5f00\u4f5c\u7528\u57df，\u5806\u4e0a\u7684 String \u88ab\u91ca\u653e<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> list =<\/span> build_list<\/span>(<\/span>)<\/span>;<\/span>
\n print_list<\/span>(<\/span>&<\/span>list)<\/span>;<\/span> \/\/ 1 2 3 Nil<\/span><\/p>\n

deref_example<\/span>(<\/span>)<\/span>;<\/span>
\n drop_example<\/span>(<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

\u77e5\u8bc6\u70b9：Rc \u2014 \u5f15\u7528\u8ba1\u6570（\u5355\u7ebf\u7a0b\u5171\u4eab\u6240\u6709\u6743）<\/h2>\n

use<\/span> std::<\/span>rc::<\/span><\/span>Rc<\/span>;<\/span><\/p>\n

\/\/ Rc<T> \u5141\u8bb8\u591a\u4e2a\u6240\u6709\u8005\u5171\u4eab\u540c\u4e00\u4efd\u6570\u636e<\/span>
\n\/\/ \u5f15\u7528\u8ba1\u6570：\u6bcf\u591a\u4e00\u4e2a Rc \u6307\u5411\u6570\u636e，\u8ba1\u6570+1<\/span>
\n\/\/ \u5f53\u8ba1\u6570\u5f52\u96f6\u65f6，\u6570\u636e\u88ab\u91ca\u653e<\/span>
\n\/\/ \u26a0\ufe0f \u53ea\u80fd\u7528\u4e8e\u5355\u7ebf\u7a0b！\u591a\u7ebf\u7a0b\u7528 Arc<T><\/span><\/p>\n

#[derive(Debug)]<\/span>
\nstruct<\/span> SharedData<\/span> {<\/span>
\n value:<\/span> String<\/span>,<\/span>
\n}<\/span><\/p>\n

fn<\/span> rc_basics<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> data =<\/span> Rc<\/span>::<\/span>new<\/span>(<\/span>SharedData<\/span> {<\/span>
\n value:<\/span> String<\/span>::<\/span>from<\/span>(<\/span>"\u5171\u4eab\u6570\u636e"<\/span>)<\/span>,<\/span>
\n }<\/span>)<\/span>;<\/span><\/p>\n

println!<\/span>(<\/span>"\u5f15\u7528\u8ba1\u6570: {}"<\/span>,<\/span> Rc<\/span>::<\/span>strong_count<\/span>(<\/span>&<\/span>data)<\/span>)<\/span>;<\/span> \/\/ 1<\/span><\/p>\n

let<\/span> clone1 =<\/span> Rc<\/span>::<\/span>clone<\/span>(<\/span>&<\/span>data)<\/span>;<\/span> \/\/ \u8ba1\u6570+1（\u4e0d\u662f\u6df1\u62f7\u8d1d！）<\/span>
\n println!<\/span>(<\/span>"\u5f15\u7528\u8ba1\u6570: {}"<\/span>,<\/span> Rc<\/span>::<\/span>strong_count<\/span>(<\/span>&<\/span>data)<\/span>)<\/span>;<\/span> \/\/ 2<\/span><\/p>\n

let<\/span> clone2 =<\/span> Rc<\/span>::<\/span>clone<\/span>(<\/span>&<\/span>data)<\/span>;<\/span> \/\/ \u8ba1\u6570+1<\/span>
\n println!<\/span>(<\/span>"\u5f15\u7528\u8ba1\u6570: {}"<\/span>,<\/span> Rc<\/span>::<\/span>strong_count<\/span>(<\/span>&<\/span>data)<\/span>)<\/span>;<\/span> \/\/ 3<\/span><\/p>\n

\/\/ \u591a\u4e2a Rc \u6307\u5411\u540c\u4e00\u4efd\u6570\u636e<\/span>
\n println!<\/span>(<\/span>"data: {}"<\/span>,<\/span> data.<\/span>value)<\/span>;<\/span>
\n println!<\/span>(<\/span>"clone1: {}"<\/span>,<\/span> clone1.<\/span>value)<\/span>;<\/span>
\n println!<\/span>(<\/span>"clone2: {}"<\/span>,<\/span> clone2.<\/span>value)<\/span>;<\/span><\/p>\n

\/\/ \u9a8c\u8bc1\u662f\u540c\u4e00\u4efd\u6570\u636e（\u6bd4\u8f83\u6307\u9488\u5730\u5740）<\/span>
\n println!<\/span>(<\/span>"\u540c\u4e00\u6570\u636e? {}"<\/span>,<\/span> Rc<\/span>::<\/span>ptr_eq<\/span>(<\/span>&<\/span>data,<\/span> &<\/span>clone1)<\/span>)<\/span>;<\/span> \/\/ true<\/span><\/p>\n

drop<\/span>(<\/span>clone2)<\/span>;<\/span>
\n println!<\/span>(<\/span>"drop clone2 \u540e\u8ba1\u6570: {}"<\/span>,<\/span> Rc<\/span>::<\/span>strong_count<\/span>(<\/span>&<\/span>data)<\/span>)<\/span>;<\/span> \/\/ 2<\/span><\/p>\n

drop<\/span>(<\/span>clone1)<\/span>;<\/span>
\n println!<\/span>(<\/span>"drop clone1 \u540e\u8ba1\u6570: {}"<\/span>,<\/span> Rc<\/span>::<\/span>strong_count<\/span>(<\/span>&<\/span>data)<\/span>)<\/span>;<\/span> \/\/ 1<\/span>
\n}<\/span><\/p>\n

\/\/ \u5b9e\u9645\u573a\u666f：\u591a\u4e2a\u7ed3\u6784\u4f53\u5171\u4eab\u540c\u4e00\u4efd\u6570\u636e<\/span>
\n#[derive(Debug)]<\/span>
\nstruct<\/span> Node<\/span> {<\/span>
\n value:<\/span> i32<\/span>,<\/span>
\n parent:<\/span> Rc<\/span><<\/span>Node<\/span>><\/span>,<\/span> \/\/ \u5171\u4eab\u7236\u8282\u70b9<\/span>
\n}<\/span><\/p>\n

fn<\/span> shared_parent<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> root =<\/span> Rc<\/span>::<\/span>new<\/span>(<\/span>Node<\/span> {<\/span> value:<\/span> 0<\/span>,<\/span> parent:<\/span> Rc<\/span>::<\/span>new<\/span>(<\/span>Node<\/span> {<\/span> value:<\/span> –<\/span>1<\/span>,<\/span> parent:<\/span> Rc<\/span>::<\/span>new<\/span>(<\/span>Node<\/span> {<\/span> value:<\/span> –<\/span>1<\/span>,<\/span> parent:<\/span> unsafe<\/span> {<\/span> Rc<\/span>::<\/span>from_raw<\/span>(<\/span>std::<\/span>ptr::<\/span><\/span>null<\/span>(<\/span>)<\/span>)<\/span> }<\/span> }<\/span>)<\/span> }<\/span>)<\/span> }<\/span>)<\/span>;<\/span>
\n \/\/ \u4e0a\u9762\u7684\u5199\u6cd5\u592a\u590d\u6742，\u5b9e\u9645\u4e2d\u7528 RefCell \u6216 Option<\/span><\/p>\n

\/\/ \u66f4\u597d\u7684\u65b9\u5f0f<\/span>
\n let<\/span> root =<\/span> Rc<\/span>::<\/span>new<\/span>(<\/span>Node2<\/span> {<\/span> value:<\/span> 0<\/span>,<\/span> children:<\/span> vec!<\/span>[<\/span>]<\/span> }<\/span>)<\/span>;<\/span>
\n \/\/ … \u89c1\u540e\u9762 RefCell \u7684\u4f8b\u5b50<\/span>
\n}<\/span><\/p>\n

\/\/ \u7b80\u5355\u793a\u4f8b：\u5171\u4eab\u914d\u7f6e<\/span>
\n#[derive(Debug)]<\/span>
\nstruct<\/span> Config<\/span> {<\/span>
\n db_host:<\/span> String<\/span>,<\/span>
\n max_connections:<\/span> u32<\/span>,<\/span>
\n}<\/span><\/p>\n

#[derive(Debug)]<\/span>
\nstruct<\/span> Service<\/span> {<\/span>
\n name:<\/span> String<\/span>,<\/span>
\n config:<\/span> Rc<\/span><<\/span>Config<\/span>><\/span>,<\/span> \/\/ \u5171\u4eab\u914d\u7f6e<\/span>
\n}<\/span><\/p>\n

fn<\/span> shared_config<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> config =<\/span> Rc<\/span>::<\/span>new<\/span>(<\/span>Config<\/span> {<\/span>
\n db_host:<\/span> String<\/span>::<\/span>from<\/span>(<\/span>"localhost"<\/span>)<\/span>,<\/span>
\n max_connections:<\/span> 100<\/span>,<\/span>
\n }<\/span>)<\/span>;<\/span><\/p>\n

let<\/span> services =<\/span> vec!<\/span>[<\/span>
\n Service<\/span> {<\/span> name:<\/span> String<\/span>::<\/span>from<\/span>(<\/span>"\u7528\u6237\u670d\u52a1"<\/span>)<\/span>,<\/span> config:<\/span> Rc<\/span>::<\/span>clone<\/span>(<\/span>&<\/span>config)<\/span> }<\/span>,<\/span>
\n Service<\/span> {<\/span> name:<\/span> String<\/span>::<\/span>from<\/span>(<\/span>"\u8ba2\u5355\u670d\u52a1"<\/span>)<\/span>,<\/span> config:<\/span> Rc<\/span>::<\/span>clone<\/span>(<\/span>&<\/span>config)<\/span> }<\/span>,<\/span>
\n Service<\/span> {<\/span> name:<\/span> String<\/span>::<\/span>from<\/span>(<\/span>"\u652f\u4ed8\u670d\u52a1"<\/span>)<\/span>,<\/span> config:<\/span> Rc<\/span>::<\/span>clone<\/span>(<\/span>&<\/span>config)<\/span> }<\/span>,<\/span>
\n ]<\/span>;<\/span><\/p>\n

for<\/span> svc in<\/span> &<\/span>services {<\/span>
\n println!<\/span>(<\/span>"{}: db={}, max_conn={}"<\/span>,<\/span> svc.<\/span>name,<\/span> svc.<\/span>config.<\/span>db_host,<\/span> svc.<\/span>config.<\/span>max_connections)<\/span>;<\/span>
\n }<\/span><\/p>\n

println!<\/span>(<\/span>"\u914d\u7f6e\u5f15\u7528\u8ba1\u6570: {}"<\/span>,<\/span> Rc<\/span>::<\/span>strong_count<\/span>(<\/span>&<\/span>config)<\/span>)<\/span>;<\/span> \/\/ 4（3\u4e2aservice + 1\u4e2a\u539f\u59cb）<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n rc_basics<\/span>(<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"—"<\/span>)<\/span>;<\/span>
\n shared_config<\/span>(<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

\u77e5\u8bc6\u70b9：RefCell \u2014 \u5185\u90e8\u53ef\u53d8\u6027<\/h2>\n

use<\/span> std::<\/span>cell::<\/span><\/span>RefCell<\/span>;<\/span><\/p>\n

\/\/ RefCell<T> \u5141\u8bb8\u5728\u4e0d\u53ef\u53d8\u5f15\u7528\u4e0b\u4fee\u6539\u6570\u636e<\/span>
\n\/\/ \u628a\u501f\u7528\u68c0\u67e5\u4ece\u7f16\u8bd1\u671f\u63a8\u8fdf\u5230\u8fd0\u884c\u671f<\/span>
\n\/\/ \u8fdd\u53cd\u501f\u7528\u89c4\u5219\u65f6\u4f1a panic（\u800c\u975e\u7f16\u8bd1\u9519\u8bef）<\/span><\/p>\n

fn<\/span> refcell_basics<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> data =<\/span> RefCell<\/span>::<\/span>new<\/span>(<\/span>vec!<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>)<\/span>;<\/span><\/p>\n

\/\/ borrow()：\u4e0d\u53ef\u53d8\u501f\u7528（\u53ef\u4ee5\u591a\u4e2a）<\/span>
\n println!<\/span>(<\/span>"\u6570\u636e: {:?}"<\/span>,<\/span> data.<\/span>borrow<\/span>(<\/span>)<\/span>)<\/span>;<\/span><\/p>\n

\/\/ borrow_mut()：\u53ef\u53d8\u501f\u7528（\u53ea\u80fd\u4e00\u4e2a，\u4e14\u4e0d\u80fd\u548c borrow \u5171\u5b58）<\/span>
\n data.<\/span>borrow_mut<\/span>(<\/span>)<\/span>.<\/span>push<\/span>(<\/span>4<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u4fee\u6539\u540e: {:?}"<\/span>,<\/span> data.<\/span>borrow<\/span>(<\/span>)<\/span>)<\/span>;<\/span><\/p>\n

\/\/ \u8fd0\u884c\u671f\u68c0\u67e5：\u8fdd\u53cd\u89c4\u5219\u4f1a panic<\/span>
\n \/\/ let r1 = data.borrow();<\/span>
\n \/\/ let r2 = data.borrow_mut(); \/\/ \u274c panic! \u540c\u65f6\u6709\u4e0d\u53ef\u53d8\u548c\u53ef\u53d8\u501f\u7528<\/span>
\n}<\/span><\/p>\n

\/\/ \u8fd0\u884c\u671f\u501f\u7528\u68c0\u67e5 vs \u7f16\u8bd1\u671f\u501f\u7528\u68c0\u67e5<\/span>
\nfn<\/span> comparison<\/span>(<\/span>)<\/span> {<\/span>
\n \/\/ \u7f16\u8bd1\u671f\u68c0\u67e5（\u666e\u901a\u5f15\u7528）<\/span>
\n let<\/span> mut<\/span> v =<\/span> vec!<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>;<\/span>
\n let<\/span> r1 =<\/span> &<\/span>v;<\/span>
\n \/\/ let r2 = &mut v; \/\/ \u274c \u7f16\u8bd1\u9519\u8bef！<\/span>
\n println!<\/span>(<\/span>"{}"<\/span>,<\/span> r1[<\/span>0<\/span>]<\/span>)<\/span>;<\/span><\/p>\n

\/\/ \u8fd0\u884c\u671f\u68c0\u67e5（RefCell）<\/span>
\n let<\/span> cell =<\/span> RefCell<\/span>::<\/span>new<\/span>(<\/span>vec!<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>)<\/span>;<\/span>
\n let<\/span> r1 =<\/span> cell.<\/span>borrow<\/span>(<\/span>)<\/span>;<\/span>
\n \/\/ let r2 = cell.borrow_mut(); \/\/ \u274c \u8fd0\u884c\u65f6 panic！<\/span>
\n println!<\/span>(<\/span>"{}"<\/span>,<\/span> r1[<\/span>0<\/span>]<\/span>)<\/span>;<\/span>
\n \/\/ \u533a\u522b：RefCell \u7684\u4ee3\u7801\u80fd\u7f16\u8bd1\u901a\u8fc7，\u4f46\u5728\u8fd0\u884c\u65f6 panic<\/span>
\n}<\/span><\/p>\n

\/\/ RefCell \u7684\u5b9e\u9645\u7528\u9014：\u5728\u53ea\u80fd\u83b7\u53d6\u4e0d\u53ef\u53d8\u5f15\u7528\u7684\u5730\u65b9\u4fee\u6539\u6570\u636e<\/span>
\n\/\/ \u4f8b\u5982：\u56de\u8c03\u51fd\u6570\u3001\u7f13\u5b58\u3001\u8ba1\u6570\u5668<\/span><\/p>\n

#[derive(Debug)]<\/span>
\nstruct<\/span> Cache<\/span> {<\/span>
\n data:<\/span> RefCell<\/span><<\/span>std::<\/span>collections::<\/span><\/span>HashMap<\/span><<\/span>String<\/span>,<\/span> String<\/span>>><\/span>,<\/span>
\n}<\/span><\/p>\n

impl<\/span> Cache<\/span> {<\/span>
\n fn<\/span> new<\/span>(<\/span>)<\/span> -><\/span> Self<\/span> {<\/span>
\n Cache<\/span> {<\/span>
\n data:<\/span> RefCell<\/span>::<\/span>new<\/span>(<\/span>std::<\/span>collections::<\/span><\/span>HashMap<\/span>::<\/span>new<\/span>(<\/span>)<\/span>)<\/span>,<\/span>
\n }<\/span>
\n }<\/span><\/p>\n

\/\/ &self \u800c\u4e0d\u662f &mut self！<\/span>
\n \/\/ \u56e0\u4e3a\u5185\u90e8\u7528 RefCell \u5b9e\u73b0\u4e86\u53ef\u53d8\u6027<\/span>
\n fn<\/span> get_or_insert<\/span>(<\/span>&<\/span>self<\/span>,<\/span> key:<\/span> &<\/span>str<\/span>,<\/span> value:<\/span> &<\/span>str<\/span>)<\/span> -><\/span> String<\/span> {<\/span>
\n let<\/span> mut<\/span> cache =<\/span> self<\/span>.<\/span>data.<\/span>borrow_mut<\/span>(<\/span>)<\/span>;<\/span>
\n if<\/span> let<\/span> Some<\/span>(<\/span>v)<\/span> =<\/span> cache.<\/span>get<\/span>(<\/span>key)<\/span> {<\/span>
\n v.<\/span>clone<\/span>(<\/span>)<\/span>
\n }<\/span> else<\/span> {<\/span>
\n cache.<\/span>insert<\/span>(<\/span>key.<\/span>to_string<\/span>(<\/span>)<\/span>,<\/span> value.<\/span>to_string<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n value.<\/span>to_string<\/span>(<\/span>)<\/span>
\n }<\/span>
\n }<\/span><\/p>\n

fn<\/span> len<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> usize<\/span> {<\/span>
\n self<\/span>.<\/span>data.<\/span>borrow<\/span>(<\/span>)<\/span>.<\/span>len<\/span>(<\/span>)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

fn<\/span> cache_example<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> cache =<\/span> Cache<\/span>::<\/span>new<\/span>(<\/span>)<\/span>;<\/span> \/\/ \u6ce8\u610f：\u4e0d\u662f mut！<\/span><\/p>\n

\/\/ \u901a\u8fc7\u4e0d\u53ef\u53d8\u5f15\u7528\u8c03\u7528"\u4fee\u6539"\u65b9\u6cd5<\/span>
\n let<\/span> val1 =<\/span> cache.<\/span>get_or_insert<\/span>(<\/span>"key1"<\/span>,<\/span> "value1"<\/span>)<\/span>;<\/span>
\n let<\/span> val2 =<\/span> cache.<\/span>get_or_insert<\/span>(<\/span>"key1"<\/span>,<\/span> "value2"<\/span>)<\/span>;<\/span> \/\/ \u5df2\u5b58\u5728，\u8fd4\u56de value1<\/span>
\n let<\/span> val3 =<\/span> cache.<\/span>get_or_insert<\/span>(<\/span>"key2"<\/span>,<\/span> "value3"<\/span>)<\/span>;<\/span><\/p>\n

println!<\/span>(<\/span>"val1: {}"<\/span>,<\/span> val1)<\/span>;<\/span> \/\/ value1<\/span>
\n println!<\/span>(<\/span>"val2: {}"<\/span>,<\/span> val2)<\/span>;<\/span> \/\/ value1（\u7f13\u5b58\u547d\u4e2d）<\/span>
\n println!<\/span>(<\/span>"val3: {}"<\/span>,<\/span> val3)<\/span>;<\/span> \/\/ value3<\/span>
\n println!<\/span>(<\/span>"\u7f13\u5b58\u5927\u5c0f: {}"<\/span>,<\/span> cache.<\/span>len<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ 2<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n refcell_basics<\/span>(<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"—"<\/span>)<\/span>;<\/span>
\n cache_example<\/span>(<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

\u77e5\u8bc6\u70b9：Rc> \u2014 \u5171\u4eab + \u53ef\u53d8<\/h2>\n

use<\/span> std::<\/span>rc::<\/span><\/span>Rc<\/span>;<\/span>
\nuse<\/span> std::<\/span>cell::<\/span><\/span>RefCell<\/span>;<\/span><\/p>\n

\/\/ Rc \u63d0\u4f9b\u5171\u4eab\u6240\u6709\u6743<\/span>
\n\/\/ RefCell \u63d0\u4f9b\u5185\u90e8\u53ef\u53d8\u6027<\/span>
\n\/\/ \u7ec4\u5408\u8d77\u6765 = \u591a\u4e2a\u6240\u6709\u8005 + \u53ef\u4fee\u6539<\/span><\/p>\n

#[derive(Debug)]<\/span>
\nstruct<\/span> TreeNode<\/span> {<\/span>
\n value:<\/span> String<\/span>,<\/span>
\n children:<\/span> RefCell<\/span><<\/span>Vec<\/span><<\/span>Rc<\/span><<\/span>TreeNode<\/span>>><\/span>><\/span>,<\/span>
\n}<\/span><\/p>\n

impl<\/span> TreeNode<\/span> {<\/span>
\n fn<\/span> new<\/span>(<\/span>value:<\/span> &<\/span>str<\/span>)<\/span> -><\/span> Rc<\/span><<\/span>Self<\/span>><\/span> {<\/span>
\n Rc<\/span>::<\/span>new<\/span>(<\/span>TreeNode<\/span> {<\/span>
\n value:<\/span> value.<\/span>to_string<\/span>(<\/span>)<\/span>,<\/span>
\n children:<\/span> RefCell<\/span>::<\/span>new<\/span>(<\/span>vec!<\/span>[<\/span>]<\/span>)<\/span>,<\/span>
\n }<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> add_child<\/span>(<\/span>parent:<\/span> &<\/span>Rc<\/span><<\/span>TreeNode<\/span>><\/span>,<\/span> child:<\/span> Rc<\/span><<\/span>TreeNode<\/span>><\/span>)<\/span> {<\/span>
\n parent.<\/span>children.<\/span>borrow_mut<\/span>(<\/span>)<\/span>.<\/span>push<\/span>(<\/span>child)<\/span>;<\/span>
\n }<\/span><\/p>\n

fn<\/span> print_tree<\/span>(<\/span>node:<\/span> &<\/span>Rc<\/span><<\/span>TreeNode<\/span>><\/span>,<\/span> indent:<\/span> usize<\/span>)<\/span> {<\/span>
\n println!<\/span>(<\/span>"{}{}"<\/span>,<\/span> " "<\/span>.<\/span>repeat<\/span>(<\/span>indent)<\/span>,<\/span> node.<\/span>value)<\/span>;<\/span>
\n for<\/span> child in<\/span> node.<\/span>children.<\/span>borrow<\/span>(<\/span>)<\/span>.<\/span>iter<\/span>(<\/span>)<\/span> {<\/span>
\n TreeNode<\/span>::<\/span>print_tree<\/span>(<\/span>child,<\/span> indent +<\/span> 2<\/span>)<\/span>;<\/span>
\n }<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

fn<\/span> tree_example<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> root =<\/span> TreeNode<\/span>::<\/span>new<\/span>(<\/span>"\u6839\u8282\u70b9"<\/span>)<\/span>;<\/span>
\n let<\/span> child1 =<\/span> TreeNode<\/span>::<\/span>new<\/span>(<\/span>"\u5b50\u8282\u70b91"<\/span>)<\/span>;<\/span>
\n let<\/span> child2 =<\/span> TreeNode<\/span>::<\/span>new<\/span>(<\/span>"\u5b50\u8282\u70b92"<\/span>)<\/span>;<\/span>
\n let<\/span> grandchild =<\/span> TreeNode<\/span>::<\/span>new<\/span>(<\/span>"\u5b59\u8282\u70b91"<\/span>)<\/span>;<\/span><\/p>\n

TreeNode<\/span>::<\/span>add_child<\/span>(<\/span>&<\/span>root,<\/span> child1.<\/span>clone<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n TreeNode<\/span>::<\/span>add_child<\/span>(<\/span>&<\/span>root,<\/span> child2.<\/span>clone<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n TreeNode<\/span>::<\/span>add_child<\/span>(<\/span>&<\/span>child1,<\/span> grandchild.<\/span>clone<\/span>(<\/span>)<\/span>)<\/span>;<\/span><\/p>\n

TreeNode<\/span>::<\/span>print_tree<\/span>(<\/span>&<\/span>root,<\/span> 0<\/span>)<\/span>;<\/span>
\n \/\/ \u6839\u8282\u70b9<\/span>
\n \/\/ \u5b50\u8282\u70b91<\/span>
\n \/\/ \u5b59\u8282\u70b91<\/span>
\n \/\/ \u5b50\u8282\u70b92<\/span>
\n}<\/span><\/p>\n

\/\/ \u5b9e\u9645\u573a\u666f：\u4e8b\u4ef6\u7cfb\u7edf<\/span>
\n#[derive(Debug)]<\/span>
\nstruct<\/span> EventBus<\/span> {<\/span>
\n listeners:<\/span> RefCell<\/span><<\/span>Vec<\/span><<\/span>Box<\/span><<\/span>dyn<\/span> Fn<\/span>(<\/span>&<\/span>str<\/span>)<\/span>>><\/span>><\/span>,<\/span>
\n}<\/span><\/p>\n

impl<\/span> EventBus<\/span> {<\/span>
\n fn<\/span> new<\/span>(<\/span>)<\/span> -><\/span> Self<\/span> {<\/span>
\n EventBus<\/span> {<\/span>
\n listeners:<\/span> RefCell<\/span>::<\/span>new<\/span>(<\/span>vec!<\/span>[<\/span>]<\/span>)<\/span>,<\/span>
\n }<\/span>
\n }<\/span><\/p>\n

fn<\/span> subscribe<\/span>(<\/span>&<\/span>self<\/span>,<\/span> callback:<\/span> Box<\/span><<\/span>dyn<\/span> Fn<\/span>(<\/span>&<\/span>str<\/span>)<\/span>><\/span>)<\/span> {<\/span>
\n self<\/span>.<\/span>listeners.<\/span>borrow_mut<\/span>(<\/span>)<\/span>.<\/span>push<\/span>(<\/span>callback)<\/span>;<\/span>
\n }<\/span><\/p>\n

fn<\/span> emit<\/span>(<\/span>&<\/span>self<\/span>,<\/span> event:<\/span> &<\/span>str<\/span>)<\/span> {<\/span>
\n for<\/span> listener in<\/span> self<\/span>.<\/span>listeners.<\/span>borrow<\/span>(<\/span>)<\/span>.<\/span>iter<\/span>(<\/span>)<\/span> {<\/span>
\n listener<\/span>(<\/span>event)<\/span>;<\/span>
\n }<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

fn<\/span> event_example<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> bus =<\/span> EventBus<\/span>::<\/span>new<\/span>(<\/span>)<\/span>;<\/span><\/p>\n

bus.<\/span>subscribe<\/span>(<\/span>Box<\/span>::<\/span>new<\/span>(<\/span>|<\/span>e|<\/span><\/span> println!<\/span>(<\/span>"\u76d1\u542c\u56681\u6536\u5230: {}"<\/span>,<\/span> e)<\/span>)<\/span>)<\/span>;<\/span>
\n bus.<\/span>subscribe<\/span>(<\/span>Box<\/span>::<\/span>new<\/span>(<\/span>|<\/span>e|<\/span><\/span> println!<\/span>(<\/span>"\u76d1\u542c\u56682\u6536\u5230: {}"<\/span>,<\/span> e)<\/span>)<\/span>)<\/span>;<\/span><\/p>\n

bus.<\/span>emit<\/span>(<\/span>"\u7528\u6237\u767b\u5f55"<\/span>)<\/span>;<\/span>
\n bus.<\/span>emit<\/span>(<\/span>"\u6570\u636e\u66f4\u65b0"<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n tree_example<\/span>(<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"—"<\/span>)<\/span>;<\/span>
\n event_example<\/span>(<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

\u77e5\u8bc6\u70b9：Cell \u2014 \u7528\u4e8e Copy \u7c7b\u578b<\/h2>\n

use<\/span> std::<\/span>cell::<\/span><\/span>Cell<\/span>;<\/span><\/p>\n

\/\/ Cell<T> \u662f RefCell<T> \u7684\u7b80\u5316\u7248<\/span>
\n\/\/ \u9002\u7528\u4e8e T: Copy \u7684\u7c7b\u578b（\u5982 i32, f64, bool）<\/span>
\n\/\/ \u4e0d\u9700\u8981 borrow\/borrow_mut，\u76f4\u63a5\u7528 get\/set<\/span>
\n\/\/ \u6027\u80fd\u66f4\u597d（\u6ca1\u6709\u8fd0\u884c\u671f\u501f\u7528\u68c0\u67e5\u5f00\u9500）<\/span><\/p>\n

fn<\/span> cell_basics<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> counter =<\/span> Cell<\/span>::<\/span>new<\/span>(<\/span>0<\/span>)<\/span>;<\/span><\/p>\n

\/\/ get()：\u590d\u5236\u51fa\u503c<\/span>
\n println!<\/span>(<\/span>"\u5f53\u524d\u503c: {}"<\/span>,<\/span> counter.<\/span>get<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ 0<\/span><\/p>\n

\/\/ set()：\u76f4\u63a5\u8bbe\u7f6e\u65b0\u503c<\/span>
\n counter.<\/span>set<\/span>(<\/span>10<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u8bbe\u7f6e\u540e: {}"<\/span>,<\/span> counter.<\/span>get<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ 10<\/span><\/p>\n

\/\/ replace()：\u8bbe\u7f6e\u65b0\u503c\u5e76\u8fd4\u56de\u65e7\u503c<\/span>
\n let<\/span> old =<\/span> counter.<\/span>replace<\/span>(<\/span>20<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u65e7\u503c: {}, \u65b0\u503c: {}"<\/span>,<\/span> old,<\/span> counter.<\/span>get<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ 10, 20<\/span><\/p>\n

\/\/ \u5e38\u7528\u65b9\u6cd5<\/span>
\n counter.<\/span>set<\/span>(<\/span>counter.<\/span>get<\/span>(<\/span>)<\/span> +<\/span> 1<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u52a01\u540e: {}"<\/span>,<\/span> counter.<\/span>get<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ 21<\/span>
\n}<\/span><\/p>\n

\/\/ \u5b9e\u9645\u573a\u666f：\u4e0d\u53ef\u53d8\u7ed3\u6784\u4f53\u4e2d\u7684\u8ba1\u6570\u5668<\/span>
\n#[derive(Debug)]<\/span>
\nstruct<\/span> RequestCounter<\/span> {<\/span>
\n name:<\/span> String<\/span>,<\/span>
\n count:<\/span> Cell<\/span><<\/span>u64<\/span>><\/span>,<\/span> \/\/ \u5185\u90e8\u53ef\u53d8，\u4f46\u7ed3\u6784\u4f53\u4e0d\u9700\u8981 mut<\/span>
\n}<\/span><\/p>\n

impl<\/span> RequestCounter<\/span> {<\/span>
\n fn<\/span> new<\/span>(<\/span>name:<\/span> &<\/span>str<\/span>)<\/span> -><\/span> Self<\/span> {<\/span>
\n RequestCounter<\/span> {<\/span>
\n name:<\/span> name.<\/span>to_string<\/span>(<\/span>)<\/span>,<\/span>
\n count:<\/span> Cell<\/span>::<\/span>new<\/span>(<\/span>0<\/span>)<\/span>,<\/span>
\n }<\/span>
\n }<\/span><\/p>\n

\/\/ &self \u800c\u975e &mut self<\/span>
\n fn<\/span> record_request<\/span>(<\/span>&<\/span>self<\/span>)<\/span> {<\/span>
\n self<\/span>.<\/span>count.<\/span>set<\/span>(<\/span>self<\/span>.<\/span>count.<\/span>get<\/span>(<\/span>)<\/span> +<\/span> 1<\/span>)<\/span>;<\/span>
\n }<\/span><\/p>\n

fn<\/span> get_count<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> u64<\/span> {<\/span>
\n self<\/span>.<\/span>count.<\/span>get<\/span>(<\/span>)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

fn<\/span> counter_example<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> counter =<\/span> RequestCounter<\/span>::<\/span>new<\/span>(<\/span>"API"<\/span>)<\/span>;<\/span><\/p>\n

\/\/ \u4e0d\u9700\u8981 mut！<\/span>
\n counter.<\/span>record_request<\/span>(<\/span>)<\/span>;<\/span>
\n counter.<\/span>record_request<\/span>(<\/span>)<\/span>;<\/span>
\n counter.<\/span>record_request<\/span>(<\/span>)<\/span>;<\/span><\/p>\n

println!<\/span>(<\/span>"{} \u8bf7\u6c42\u6b21\u6570: {}"<\/span>,<\/span> counter.<\/span>name,<\/span> counter.<\/span>get_count<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ 3<\/span>
\n}<\/span><\/p>\n

\/\/ Cell \u7684\u5e38\u89c1\u6a21\u5f0f：\u7528 update_with \u7b80\u5316<\/span>
\nfn<\/span> cell_update<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> val =<\/span> Cell<\/span>::<\/span>new<\/span>(<\/span>10<\/span>)<\/span>;<\/span><\/p>\n

\/\/ \u5e38\u89c1\u64cd\u4f5c：\u8bfb\u53d6 -> \u4fee\u6539 -> \u5199\u56de<\/span>
\n val.<\/span>set<\/span>(<\/span>val.<\/span>get<\/span>(<\/span>)<\/span> *<\/span> 2<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u7ffb\u500d: {}"<\/span>,<\/span> val.<\/span>get<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ 20<\/span><\/p>\n

val.<\/span>set<\/span>(<\/span>val.<\/span>get<\/span>(<\/span>)<\/span> +<\/span> 5<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u52a05: {}"<\/span>,<\/span> val.<\/span>get<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ 25<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n cell_basics<\/span>(<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"—"<\/span>)<\/span>;<\/span>
\n counter_example<\/span>(<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"—"<\/span>)<\/span>;<\/span>
\n cell_update<\/span>(<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

\u77e5\u8bc6\u70b9：Weak \u2014 \u5f31\u5f15\u7528（\u6253\u7834\u5faa\u73af\u5f15\u7528）<\/h2>\n

use<\/span> std::<\/span>rc::<\/span><\/span>Rc<\/span>;<\/span>
\nuse<\/span> std::<\/span>rc::<\/span><\/span>Weak<\/span>;<\/span>
\nuse<\/span> std::<\/span>cell::<\/span><\/span>RefCell<\/span>;<\/span><\/p>\n

\/\/ Weak<T> \u7c7b\u4f3c Rc<T>，\u4f46\u4e0d\u589e\u52a0\u5f3a\u5f15\u7528\u8ba1\u6570<\/span>
\n\/\/ \u4e0d\u4f1a\u963b\u6b62\u6570\u636e\u88ab\u91ca\u653e<\/span>
\n\/\/ \u7528 upgrade() \u5c1d\u8bd5\u83b7\u53d6 Rc<T>（\u53ef\u80fd\u8fd4\u56de None）<\/span><\/p>\n

\/\/ \u5faa\u73af\u5f15\u7528\u95ee\u9898：<\/span>
\n\/\/ A -> B -> A \u4f1a\u5bfc\u81f4\u5f15\u7528\u8ba1\u6570\u6c38\u8fdc\u4e0d\u5f52\u96f6，\u5185\u5b58\u6cc4\u6f0f<\/span><\/p>\n

#[derive(Debug)]<\/span>
\nstruct<\/span> Node<\/span> {<\/span>
\n value:<\/span> i32<\/span>,<\/span>
\n next:<\/span> RefCell<\/span><<\/span>Option<\/span><<\/span>Rc<\/span><<\/span>Node<\/span>>><\/span>><\/span>,<\/span>
\n prev:<\/span> RefCell<\/span><<\/span>Option<\/span><<\/span>Weak<\/span><<\/span>Node<\/span>>><\/span>><\/span>,<\/span> \/\/ \u7528 Weak \u6253\u7834\u5faa\u73af！<\/span>
\n}<\/span><\/p>\n

impl<\/span> Node<\/span> {<\/span>
\n fn<\/span> new<\/span>(<\/span>value:<\/span> i32<\/span>)<\/span> -><\/span> Rc<\/span><<\/span>Self<\/span>><\/span> {<\/span>
\n Rc<\/span>::<\/span>new<\/span>(<\/span>Node<\/span> {<\/span>
\n value,<\/span>
\n next:<\/span> RefCell<\/span>::<\/span>new<\/span>(<\/span>None<\/span>)<\/span>,<\/span>
\n prev:<\/span> RefCell<\/span>::<\/span>new<\/span>(<\/span>None<\/span>)<\/span>,<\/span>
\n }<\/span>)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

fn<\/span> doubly_linked_list<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> node1 =<\/span> Node<\/span>::<\/span>new<\/span>(<\/span>1<\/span>)<\/span>;<\/span>
\n let<\/span> node2 =<\/span> Node<\/span>::<\/span>new<\/span>(<\/span>2<\/span>)<\/span>;<\/span>
\n let<\/span> node3 =<\/span> Node<\/span>::<\/span>new<\/span>(<\/span>3<\/span>)<\/span>;<\/span><\/p>\n

\/\/ 1 -> 2 -> 3<\/span>
\n *<\/span>node1.<\/span>next.<\/span>borrow_mut<\/span>(<\/span>)<\/span> =<\/span> Some<\/span>(<\/span>Rc<\/span>::<\/span>clone<\/span>(<\/span>&<\/span>node2)<\/span>)<\/span>;<\/span>
\n *<\/span>node2.<\/span>next.<\/span>borrow_mut<\/span>(<\/span>)<\/span> =<\/span> Some<\/span>(<\/span>Rc<\/span>::<\/span>clone<\/span>(<\/span>&<\/span>node3)<\/span>)<\/span>;<\/span><\/p>\n

\/\/ 3 -> 2 -> 1（\u7528 Weak \u907f\u514d\u5faa\u73af\u5f15\u7528）<\/span>
\n *<\/span>node3.<\/span>prev.<\/span>borrow_mut<\/span>(<\/span>)<\/span> =<\/span> Some<\/span>(<\/span>Rc<\/span>::<\/span>downgrade<\/span>(<\/span>&<\/span>node2)<\/span>)<\/span>;<\/span>
\n *<\/span>node2.<\/span>prev.<\/span>borrow_mut<\/span>(<\/span>)<\/span> =<\/span> Some<\/span>(<\/span>Rc<\/span>::<\/span>downgrade<\/span>(<\/span>&<\/span>node1)<\/span>)<\/span>;<\/span><\/p>\n

\/\/ \u6b63\u5411\u904d\u5386<\/span>
\n print!<\/span>(<\/span>"\u6b63\u5411: "<\/span>)<\/span>;<\/span>
\n let<\/span> mut<\/span> current =<\/span> Some<\/span>(<\/span>Rc<\/span>::<\/span>clone<\/span>(<\/span>&<\/span>node1)<\/span>)<\/span>;<\/span>
\n while<\/span> let<\/span> Some<\/span>(<\/span>node)<\/span> =<\/span> current {<\/span>
\n print!<\/span>(<\/span>"{} "<\/span>,<\/span> node.<\/span>value)<\/span>;<\/span>
\n current =<\/span> node.<\/span>next.<\/span>borrow<\/span>(<\/span>)<\/span>.<\/span>clone<\/span>(<\/span>)<\/span>;<\/span>
\n }<\/span>
\n println!<\/span>(<\/span>)<\/span>;<\/span><\/p>\n

\/\/ \u53cd\u5411\u904d\u5386<\/span>
\n print!<\/span>(<\/span>"\u53cd\u5411: "<\/span>)<\/span>;<\/span>
\n let<\/span> mut<\/span> current =<\/span> Some<\/span>(<\/span>Rc<\/span>::<\/span>clone<\/span>(<\/span>&<\/span>node3)<\/span>)<\/span>;<\/span>
\n while<\/span> let<\/span> Some<\/span>(<\/span>node)<\/span> =<\/span> current {<\/span>
\n print!<\/span>(<\/span>"{} "<\/span>,<\/span> node.<\/span>value)<\/span>;<\/span>
\n current =<\/span> node.<\/span>prev.<\/span>borrow<\/span>(<\/span>)<\/span>.<\/span>as_ref<\/span>(<\/span>)<\/span>
\n .<\/span>and_then<\/span>(<\/span>|<\/span>weak|<\/span><\/span> weak.<\/span>upgrade<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n }<\/span>
\n println!<\/span>(<\/span>)<\/span>;<\/span><\/p>\n

\/\/ \u9a8c\u8bc1\u5f15\u7528\u8ba1\u6570<\/span>
\n println!<\/span>(<\/span>"node1 \u5f3a\u5f15\u7528: {}, \u5f31\u5f15\u7528: {}"<\/span>,<\/span>
\n Rc<\/span>::<\/span>strong_count<\/span>(<\/span>&<\/span>node1)<\/span>,<\/span>
\n Rc<\/span>::<\/span>weak_count<\/span>(<\/span>&<\/span>node1)<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"node2 \u5f3a\u5f15\u7528: {}, \u5f31\u5f15\u7528: {}"<\/span>,<\/span>
\n Rc<\/span>::<\/span>strong_count<\/span>(<\/span>&<\/span>node2)<\/span>,<\/span>
\n Rc<\/span>::<\/span>weak_count<\/span>(<\/span>&<\/span>node2)<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

\/\/ Weak \u7684\u5b9e\u9645\u7528\u9014：\u7f13\u5b58<\/span>
\nuse<\/span> std::<\/span>collections::<\/span><\/span>HashMap<\/span>;<\/span><\/p>\n

struct<\/span> ImageCache<\/span> {<\/span>
\n cache:<\/span> RefCell<\/span><<\/span>HashMap<\/span><<\/span>String<\/span>,<\/span> Weak<\/span><<\/span>Vec<\/span><<\/span>u8<\/span>>><\/span>>><\/span>,<\/span>
\n}<\/span><\/p>\n

impl<\/span> ImageCache<\/span> {<\/span>
\n fn<\/span> new<\/span>(<\/span>)<\/span> -><\/span> Self<\/span> {<\/span>
\n ImageCache<\/span> {<\/span>
\n cache:<\/span> RefCell<\/span>::<\/span>new<\/span>(<\/span>HashMap<\/span>::<\/span>new<\/span>(<\/span>)<\/span>)<\/span>,<\/span>
\n }<\/span>
\n }<\/span><\/p>\n

fn<\/span> get<\/span>(<\/span>&<\/span>self<\/span>,<\/span> key:<\/span> &<\/span>str<\/span>)<\/span> -><\/span> Option<\/span><<\/span>Rc<\/span><<\/span>Vec<\/span><<\/span>u8<\/span>>><\/span>><\/span> {<\/span>
\n let<\/span> cache =<\/span> self<\/span>.<\/span>cache.<\/span>borrow<\/span>(<\/span>)<\/span>;<\/span>
\n cache.<\/span>get<\/span>(<\/span>key)<\/span>.<\/span>and_then<\/span>(<\/span>|<\/span>weak|<\/span><\/span> {<\/span>
\n weak.<\/span>upgrade<\/span>(<\/span>)<\/span> \/\/ \u5982\u679c\u6570\u636e\u8fd8\u5728，\u8fd4\u56de Some(Rc)<\/span>
\n \/\/ \u5982\u679c\u5df2\u88ab\u91ca\u653e，\u8fd4\u56de None<\/span>
\n }<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> insert<\/span>(<\/span>&<\/span>self<\/span>,<\/span> key:<\/span> String<\/span>,<\/span> data:<\/span> Rc<\/span><<\/span>Vec<\/span><<\/span>u8<\/span>>><\/span>)<\/span> {<\/span>
\n let<\/span> weak =<\/span> Rc<\/span>::<\/span>downgrade<\/span>(<\/span>&<\/span>data)<\/span>;<\/span>
\n self<\/span>.<\/span>cache.<\/span>borrow_mut<\/span>(<\/span>)<\/span>.<\/span>insert<\/span>(<\/span>key,<\/span> weak)<\/span>;<\/span>
\n }<\/span><\/p>\n

fn<\/span> cleanup<\/span>(<\/span>&<\/span>self<\/span>)<\/span> {<\/span>
\n \/\/ \u79fb\u9664\u5df2\u5931\u6548\u7684\u5f31\u5f15\u7528<\/span>
\n self<\/span>.<\/span>cache.<\/span>borrow_mut<\/span>(<\/span>)<\/span>.<\/span>retain<\/span>(<\/span>|<\/span>_,<\/span> weak|<\/span><\/span> weak.<\/span>strong_count<\/span>(<\/span>)<\/span> ><\/span> 0<\/span>)<\/span>;<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

fn<\/span> cache_example<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> cache =<\/span> ImageCache<\/span>::<\/span>new<\/span>(<\/span>)<\/span>;<\/span><\/p>\n

\/\/ \u63d2\u5165\u4e00\u4e9b\u6570\u636e<\/span>
\n let<\/span> img1 =<\/span> Rc<\/span>::<\/span>new<\/span>(<\/span>vec!<\/span>[<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>]<\/span>)<\/span>;<\/span>
\n let<\/span> img2 =<\/span> Rc<\/span>::<\/span>new<\/span>(<\/span>vec!<\/span>[<\/span>4<\/span>,<\/span> 5<\/span>,<\/span> 6<\/span>]<\/span>)<\/span>;<\/span><\/p>\n

cache.<\/span>insert<\/span>(<\/span>"img1.png"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>,<\/span> img1.<\/span>clone<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n cache.<\/span>insert<\/span>(<\/span>"img2.png"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>,<\/span> img2.<\/span>clone<\/span>(<\/span>)<\/span>)<\/span>;<\/span><\/p>\n

\/\/ \u80fd\u83b7\u53d6\u5230<\/span>
\n println!<\/span>(<\/span>"img1: {:?}"<\/span>,<\/span> cache.<\/span>get<\/span>(<\/span>"img1.png"<\/span>)<\/span>.<\/span>map<\/span>(<\/span>|<\/span>d|<\/span><\/span> d.<\/span>len<\/span>(<\/span>)<\/span>)<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"img2: {:?}"<\/span>,<\/span> cache.<\/span>get<\/span>(<\/span>"img2.png"<\/span>)<\/span>.<\/span>map<\/span>(<\/span>|<\/span>d|<\/span><\/span> d.<\/span>len<\/span>(<\/span>)<\/span>)<\/span>)<\/span>;<\/span><\/p>\n

\/\/ \u91ca\u653e img1 \u7684\u5f3a\u5f15\u7528<\/span>
\n drop<\/span>(<\/span>img1)<\/span>;<\/span><\/p>\n

\/\/ img1 \u5df2\u88ab\u91ca\u653e，\u83b7\u53d6\u8fd4\u56de None<\/span>
\n println!<\/span>(<\/span>"img1 (\u5df2\u91ca\u653e): {:?}"<\/span>,<\/span> cache.<\/span>get<\/span>(<\/span>"img1.png"<\/span>)<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"img2 (\u4ecd\u5728): {:?}"<\/span>,<\/span> cache.<\/span>get<\/span>(<\/span>"img2.png"<\/span>)<\/span>)<\/span>;<\/span><\/p>\n

\/\/ \u6e05\u7406\u5931\u6548\u7684\u5f31\u5f15\u7528<\/span>
\n cache.<\/span>cleanup<\/span>(<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n doubly_linked_list<\/span>(<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"—"<\/span>)<\/span>;<\/span>
\n cache_example<\/span>(<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

\u77e5\u8bc6\u70b9：\u5404\u79cd\u667a\u80fd\u6307\u9488\u4e0e\u5185\u90e8\u53ef\u53d8\u6027\u7c7b\u578b\u5bf9\u6bd4<\/h2>\n

\/\/ === \u6240\u6709\u6743\u6a21\u578b\u5bf9\u6bd4 ===<\/span><\/p>\n

\/\/ \u5355\u4e00\u6240\u6709\u6743：<\/span>
\n\/\/ Box<T> \u2014 \u5806\u4e0a\u5206\u914d，\u5355\u4e00\u6240\u6709\u8005<\/span>
\n\/\/ String \u2014 \u5806\u4e0a\u5b57\u7b26\u4e32，\u5355\u4e00\u6240\u6709\u8005<\/span>
\n\/\/ Vec<T> \u2014 \u5806\u4e0a\u6570\u7ec4，\u5355\u4e00\u6240\u6709\u8005<\/span><\/p>\n

\/\/ \u5171\u4eab\u6240\u6709\u6743（\u4e0d\u53ef\u53d8）：<\/span>
\n\/\/ Rc<T> \u2014 \u5355\u7ebf\u7a0b\u5f15\u7528\u8ba1\u6570<\/span>
\n\/\/ Arc<T> \u2014 \u591a\u7ebf\u7a0b\u5f15\u7528\u8ba1\u6570（\u539f\u5b50\u64cd\u4f5c）<\/span><\/p>\n

\/\/ \u5185\u90e8\u53ef\u53d8\u6027（\u5355\u7ebf\u7a0b）：<\/span>
\n\/\/ Cell<T> \u2014 \u7528\u4e8e Copy \u7c7b\u578b，\u65e0\u8fd0\u884c\u671f\u68c0\u67e5<\/span>
\n\/\/ RefCell<T> \u2014 \u7528\u4e8e\u4efb\u610f\u7c7b\u578b，\u8fd0\u884c\u671f\u501f\u7528\u68c0\u67e5<\/span>
\n\/\/ UnsafeCell<T> \u2014 \u6700\u5e95\u5c42，\u65e0\u68c0\u67e5（unsafe）<\/span><\/p>\n

\/\/ \u5171\u4eab + \u53ef\u53d8（\u5355\u7ebf\u7a0b）：<\/span>
\n\/\/ Rc<RefCell<T>> \u2014 \u591a\u4e2a\u6240\u6709\u8005 + \u53ef\u4fee\u6539<\/span>
\n\/\/ Rc<Cell<T>> \u2014 \u591a\u4e2a\u6240\u6709\u8005 + \u53ef\u4fee\u6539（Copy\u7c7b\u578b）<\/span><\/p>\n

\/\/ \u5171\u4eab + \u53ef\u53d8（\u591a\u7ebf\u7a0b）：<\/span>
\n\/\/ Arc<Mutex<T>> \u2014 \u591a\u4e2a\u6240\u6709\u8005 + \u4e92\u65a5\u4fee\u6539<\/span>
\n\/\/ Arc<RwLock<T>> \u2014 \u591a\u4e2a\u6240\u6709\u8005 + \u8bfb\u5199\u9501<\/span><\/p>\n

\/\/ \u5f31\u5f15\u7528：<\/span>
\n\/\/ Weak<T> \u2014 Rc \u7684\u5f31\u5f15\u7528\u7248\u672c<\/span>
\n\/\/ Arc \u4e5f\u6709 Weak \u2014 Arc::downgrade()<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n println!<\/span>(<\/span>"\u667a\u80fd\u6307\u9488\u901f\u67e5:"<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>" \u5806\u5206\u914d: Box<T>"<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>" \u5171\u4eab(\u53ea\u8bfb): Rc<T> \/ Arc<T>"<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>" \u5185\u90e8\u53ef\u53d8: Cell<T> \/ RefCell<T>"<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>" \u5171\u4eab+\u53ef\u53d8: Rc<RefCell<T>> \/ Arc<Mutex<T>>"<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>" \u5f31\u5f15\u7528: Weak<T>"<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>""<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u9009\u62e9\u6307\u5357:"<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>" \u9700\u8981\u5806\u5206\u914d？ \u2192 Box<T>"<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>" \u9700\u8981\u5171\u4eab\u53ea\u8bfb？ \u2192 Rc<T>（\u5355\u7ebf\u7a0b）\/ Arc<T>（\u591a\u7ebf\u7a0b）"<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>" \u9700\u8981\u5185\u90e8\u4fee\u6539？ \u2192 Cell<T>（Copy\u7c7b\u578b）\/ RefCell<T>（\u4efb\u610f\u7c7b\u578b）"<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>" \u9700\u8981\u5171\u4eab+\u4fee\u6539？ \u2192 Rc<RefCell<T>>（\u5355\u7ebf\u7a0b）\/ Arc<Mutex<T>>（\u591a\u7ebf\u7a0b）"<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>" \u907f\u514d\u5faa\u73af\u5f15\u7528？ \u2192 Weak<T>"<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

\u6838\u5fc3\u89c4\u5219<\/h2>\n

\u7c7b\u578b \u6240\u6709\u6743 \u53ef\u53d8\u6027 \u7ebf\u7a0b\u5b89\u5168 \u5f00\u9500
\nBox \u5355\u4e00 \u9700 mut \u2705 \u6700\u4f4e
\nRc \u5171\u4eab \u4e0d\u53ef\u53d8 \u274c \u4f4e（\u8ba1\u6570）
\nArc \u5171\u4eab \u4e0d\u53ef\u53d8 \u2705 \u4e2d（\u539f\u5b50\u8ba1\u6570）
\nCell \u5355\u4e00 \u5185\u90e8\u53ef\u53d8 \u274c \u6700\u4f4e（Copy）
\nRefCell \u5355\u4e00 \u5185\u90e8\u53ef\u53d8 \u274c \u4e2d（\u8fd0\u884c\u671f\u68c0\u67e5）
\nRc<RefCell> \u5171\u4eab \u5185\u90e8\u53ef\u53d8 \u274c \u4e2d+\u4e2d
\nArc<Mutex> \u5171\u4eab \u5185\u90e8\u53ef\u53d8 \u2705 \u9ad8（\u539f\u5b50+\u9501）
\nWeak \u4e0d\u62e5\u6709 \u2014 \u8ddf\u968f Rc\/Arc \u4f4e<\/p>\n

\u52a8\u624b\u8bd5\u8bd5<\/h2>\n

\u8865\u5168\u4e0b\u9762\u7684\u4ee3\u7801：<\/h3>\n

use<\/span> std::<\/span>rc::<\/span><\/span>Rc<\/span>;<\/span>
\nuse<\/span> std::<\/span>cell::<\/span><\/span>RefCell<\/span>;<\/span>
\nuse<\/span> std::<\/span>cell::<\/span><\/span>Cell<\/span>;<\/span>
\nuse<\/span> std::<\/span>collections::<\/span><\/span>HashMap<\/span>;<\/span><\/p>\n

\/\/ === \u9898\u76ee1：\u4efb\u52a1\u7ba1\u7406\u5668 ===<\/span>
\n\/\/ \u8865\u5168：\u5b9e\u73b0 TaskManager，\u4f7f\u7528\u5185\u90e8\u53ef\u53d8\u6027<\/span>
\n\/\/ – tasks \u5b57\u6bb5\u7528 RefCell<Vec<String>> \u5b58\u50a8<\/span>
\n\/\/ – completed_count \u5b57\u6bb5\u7528 Cell<u32> \u7edf\u8ba1\u5b8c\u6210\u6570<\/span>
\n\/\/ – add_task(&self, task: &str)：\u6dfb\u52a0\u4efb\u52a1<\/span>
\n\/\/ – complete_task(&self, index: usize) -> bool：<\/span>
\n\/\/ \u5982\u679c index \u6709\u6548，\u79fb\u9664\u8be5\u4efb\u52a1\u5e76\u589e\u52a0 completed_count，\u8fd4\u56de true<\/span>
\n\/\/ \u5982\u679c index \u65e0\u6548，\u8fd4\u56de false<\/span>
\n\/\/ – pending_count(&self) -> usize：\u8fd4\u56de\u5f85\u5b8c\u6210\u4efb\u52a1\u6570<\/span>
\n\/\/ – total_completed(&self) -> u32：\u8fd4\u56de\u5df2\u5b8c\u6210\u603b\u6570<\/span><\/p>\n

struct<\/span> TaskManager<\/span> {<\/span>
\n \/\/ \u8865\u5168\u5b57\u6bb5<\/span>
\n}<\/span><\/p>\n

impl<\/span> TaskManager<\/span> {<\/span>
\n fn<\/span> new<\/span>(<\/span>)<\/span> -><\/span> Self<\/span> {<\/span>
\n \/\/ \u8865\u5168<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> add_task<\/span>(<\/span>&<\/span>self<\/span>,<\/span> task:<\/span> &<\/span>str<\/span>)<\/span> {<\/span>
\n \/\/ \u8865\u5168<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> complete_task<\/span>(<\/span>&<\/span>self<\/span>,<\/span> index:<\/span> usize<\/span>)<\/span> -><\/span> bool<\/span> {<\/span>
\n \/\/ \u8865\u5168<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> pending_count<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> usize<\/span> {<\/span>
\n \/\/ \u8865\u5168<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> total_completed<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> u32<\/span> {<\/span>
\n \/\/ \u8865\u5168<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

\/\/ === \u9898\u76ee2：\u5171\u4eab\u914d\u7f6e + \u7edf\u8ba1 ===<\/span>
\n\/\/ \u8865\u5168：\u5b9e\u73b0 SharedConfig<\/span>
\n\/\/ – \u7528 Rc \u5171\u4eab\u914d\u7f6e\u6570\u636e<\/span>
\n\/\/ – \u7528 Cell \u8bb0\u5f55\u8bbf\u95ee\u6b21\u6570<\/span>
\n\/\/ – get(&self, key: &str) -> Option<String>：\u83b7\u53d6\u914d\u7f6e\u503c，\u589e\u52a0\u8bbf\u95ee\u8ba1\u6570<\/span>
\n\/\/ – access_count(&self) -> u64：\u8fd4\u56de\u8bbf\u95ee\u6b21\u6570<\/span><\/p>\n

struct<\/span> SharedConfig<\/span> {<\/span>
\n data:<\/span> Rc<\/span><<\/span>HashMap<\/span><<\/span>String<\/span>,<\/span> String<\/span>>><\/span>,<\/span>
\n access_count:<\/span> Cell<\/span><<\/span>u64<\/span>><\/span>,<\/span>
\n}<\/span><\/p>\n

impl<\/span> SharedConfig<\/span> {<\/span>
\n fn<\/span> new<\/span>(<\/span>)<\/span> -><\/span> Self<\/span> {<\/span>
\n \/\/ \u8865\u5168：\u521b\u5efa\u4e00\u4e2a\u7a7a\u7684 SharedConfig<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> with_data<\/span>(<\/span>data:<\/span> HashMap<\/span><<\/span>String<\/span>,<\/span> String<\/span>><\/span>)<\/span> -><\/span> Self<\/span> {<\/span>
\n \/\/ \u8865\u5168：\u7528\u7ed9\u5b9a\u7684\u6570\u636e\u521b\u5efa SharedConfig<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> get<\/span>(<\/span>&<\/span>self<\/span>,<\/span> key:<\/span> &<\/span>str<\/span>)<\/span> -><\/span> Option<\/span><<\/span>String<\/span>><\/span> {<\/span>
\n \/\/ \u8865\u5168：\u67e5\u627e key，\u5982\u679c\u627e\u5230\u5219\u589e\u52a0\u8bbf\u95ee\u8ba1\u6570\u5e76\u8fd4\u56de Some(value)<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> access_count<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> u64<\/span> {<\/span>
\n \/\/ \u8865\u5168<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> clone_ref<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> Self<\/span> {<\/span>
\n \/\/ \u8865\u5168：\u514b\u9686 Rc（\u5171\u4eab\u6570\u636e），\u4f46 access_count \u91cd\u7f6e\u4e3a 0<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

\/\/ === \u9898\u76ee3：\u6811\u7ed3\u6784 + \u7236\u8282\u70b9\u5f31\u5f15\u7528 ===<\/span>
\n\/\/ \u8865\u5168：\u5b9e\u73b0\u5e26\u7236\u8282\u70b9\u5f15\u7528\u7684\u6811\u8282\u70b9<\/span><\/p>\n

struct<\/span> TreeNode<\/span> {<\/span>
\n value:<\/span> String<\/span>,<\/span>
\n children:<\/span> RefCell<\/span><<\/span>Vec<\/span><<\/span>Rc<\/span><<\/span>TreeNode<\/span>>><\/span>><\/span>,<\/span>
\n parent:<\/span> RefCell<\/span><<\/span>Option<\/span><<\/span>std::<\/span>rc::<\/span><\/span>Weak<\/span><<\/span>TreeNode<\/span>>><\/span>><\/span>,<\/span> \/\/ \u5f31\u5f15\u7528<\/span>
\n}<\/span><\/p>\n

impl<\/span> TreeNode<\/span> {<\/span>
\n fn<\/span> new<\/span>(<\/span>value:<\/span> &<\/span>str<\/span>)<\/span> -><\/span> Rc<\/span><<\/span>Self<\/span>><\/span> {<\/span>
\n \/\/ \u8865\u5168<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> add_child<\/span>(<\/span>parent:<\/span> &<\/span>Rc<\/span><<\/span>TreeNode<\/span>><\/span>,<\/span> child:<\/span> Rc<\/span><<\/span>TreeNode<\/span>><\/span>)<\/span> {<\/span>
\n \/\/ \u8865\u5168：\u6dfb\u52a0\u5b50\u8282\u70b9，\u5e76\u8bbe\u7f6e\u5b50\u8282\u70b9\u7684 parent \u4e3a parent \u7684\u5f31\u5f15\u7528<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> get_parent_value<\/span>(<\/span>node:<\/span> &<\/span>Rc<\/span><<\/span>TreeNode<\/span>><\/span>)<\/span> -><\/span> Option<\/span><<\/span>String<\/span>><\/span> {<\/span>
\n \/\/ \u8865\u5168：\u83b7\u53d6\u7236\u8282\u70b9\u7684\u503c（\u901a\u8fc7\u5f31\u5f15\u7528\u7684 upgrade）<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> get_root<\/span>(<\/span>node:<\/span> &<\/span>Rc<\/span><<\/span>TreeNode<\/span>><\/span>)<\/span> -><\/span> Rc<\/span><<\/span>TreeNode<\/span>><\/span> {<\/span>
\n \/\/ \u8865\u5168：\u5411\u4e0a\u904d\u5386\u627e\u5230\u6839\u8282\u70b9<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

impl<\/span> std::<\/span>fmt::<\/span><\/span>Debug<\/span> for<\/span> TreeNode<\/span> {<\/span>
\n fn<\/span> fmt<\/span>(<\/span>&<\/span>self<\/span>,<\/span> f:<\/span> &<\/span>mut<\/span> std::<\/span>fmt::<\/span><\/span>Formatter<\/span><<\/span>'_<\/span>><\/span>)<\/span> -><\/span> std::<\/span>fmt::<\/span><\/span>Result<\/span> {<\/span>
\n write!<\/span>(<\/span>f,<\/span> "TreeNode({})"<\/span>,<\/span> self<\/span>.<\/span>value)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n \/\/ === \u6d4b\u8bd5 TaskManager ===<\/span>
\n let<\/span> tm =<\/span> TaskManager<\/span>::<\/span>new<\/span>(<\/span>)<\/span>;<\/span><\/p>\n

tm.<\/span>add_task<\/span>(<\/span>"\u5199\u62a5\u544a"<\/span>)<\/span>;<\/span>
\n tm.<\/span>add_task<\/span>(<\/span>"\u5f00\u4f1a"<\/span>)<\/span>;<\/span>
\n tm.<\/span>add_task<\/span>(<\/span>"\u4ee3\u7801\u5ba1\u67e5"<\/span>)<\/span>;<\/span>
\n tm.<\/span>add_task<\/span>(<\/span>"\u4feebug"<\/span>)<\/span>;<\/span><\/p>\n

println!<\/span>(<\/span>"\u5f85\u5b8c\u6210: {}"<\/span>,<\/span> tm.<\/span>pending_count<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u671f\u671b: 4<\/span>
\n println!<\/span>(<\/span>"\u5df2\u5b8c\u6210: {}"<\/span>,<\/span> tm.<\/span>total_completed<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u671f\u671b: 0<\/span><\/p>\n

assert!<\/span>(<\/span>tm.<\/span>complete_task<\/span>(<\/span>1<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u5b8c\u6210"\u5f00\u4f1a"<\/span>
\n assert!<\/span>(<\/span>tm.<\/span>complete_task<\/span>(<\/span>0<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u5b8c\u6210"\u5199\u62a5\u544a"（\u539findex 0，\u56e0\u4e3a"\u5f00\u4f1a"\u88ab\u79fb\u9664\u540e"\u5199\u62a5\u544a"\u53d8\u6210\u4e86index 0）<\/span>
\n assert!<\/span>(<\/span>!<\/span>tm.<\/span>complete_task<\/span>(<\/span>10<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u65e0\u6548\u7d22\u5f15<\/span><\/p>\n

println!<\/span>(<\/span>"\u5f85\u5b8c\u6210: {}"<\/span>,<\/span> tm.<\/span>pending_count<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u671f\u671b: 2<\/span>
\n println!<\/span>(<\/span>"\u5df2\u5b8c\u6210: {}"<\/span>,<\/span> tm.<\/span>total_completed<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u671f\u671b: 2<\/span><\/p>\n

\/\/ === \u6d4b\u8bd5 SharedConfig ===<\/span>
\n let<\/span> mut<\/span> data =<\/span> HashMap<\/span>::<\/span>new<\/span>(<\/span>)<\/span>;<\/span>
\n data.<\/span>insert<\/span>(<\/span>"host"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>,<\/span> "localhost"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n data.<\/span>insert<\/span>(<\/span>"port"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>,<\/span> "5432"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n data.<\/span>insert<\/span>(<\/span>"db"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>,<\/span> "mydb"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>)<\/span>;<\/span><\/p>\n

let<\/span> config =<\/span> SharedConfig<\/span>::<\/span>with_data<\/span>(<\/span>data)<\/span>;<\/span>
\n let<\/span> config2 =<\/span> config.<\/span>clone_ref<\/span>(<\/span>)<\/span>;<\/span><\/p>\n

println!<\/span>(<\/span>"host: {:?}"<\/span>,<\/span> config.<\/span>get<\/span>(<\/span>"host"<\/span>)<\/span>)<\/span>;<\/span> \/\/ Some("localhost")<\/span>
\n println!<\/span>(<\/span>"port: {:?}"<\/span>,<\/span> config.<\/span>get<\/span>(<\/span>"port"<\/span>)<\/span>)<\/span>;<\/span> \/\/ Some("5432")<\/span>
\n println!<\/span>(<\/span>"missing: {:?}"<\/span>,<\/span> config.<\/span>get<\/span>(<\/span>"missing"<\/span>)<\/span>)<\/span>;<\/span> \/\/ None<\/span>
\n println!<\/span>(<\/span>"config \u8bbf\u95ee\u6b21\u6570: {}"<\/span>,<\/span> config.<\/span>access_count<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u671f\u671b: 2<\/span>
\n println!<\/span>(<\/span>"config2 \u8bbf\u95ee\u6b21\u6570: {}"<\/span>,<\/span> config2.<\/span>access_count<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u671f\u671b: 0（\u72ec\u7acb\u7684\u8ba1\u6570）<\/span><\/p>\n

\/\/ === \u6d4b\u8bd5 TreeNode ===<\/span>
\n let<\/span> root =<\/span> TreeNode<\/span>::<\/span>new<\/span>(<\/span>"\u6839"<\/span>)<\/span>;<\/span>
\n let<\/span> child1 =<\/span> TreeNode<\/span>::<\/span>new<\/span>(<\/span>"\u5b501"<\/span>)<\/span>;<\/span>
\n let<\/span> child2 =<\/span> TreeNode<\/span>::<\/span>new<\/span>(<\/span>"\u5b502"<\/span>)<\/span>;<\/span>
\n let<\/span> grandchild =<\/span> TreeNode<\/span>::<\/span>new<\/span>(<\/span>"\u5b591"<\/span>)<\/span>;<\/span><\/p>\n

TreeNode<\/span>::<\/span>add_child<\/span>(<\/span>&<\/span>root,<\/span> child1.<\/span>clone<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n TreeNode<\/span>::<\/span>add_child<\/span>(<\/span>&<\/span>root,<\/span> child2.<\/span>clone<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n TreeNode<\/span>::<\/span>add_child<\/span>(<\/span>&<\/span>child1,<\/span> grandchild.<\/span>clone<\/span>(<\/span>)<\/span>)<\/span>;<\/span><\/p>\n

\/\/ \u6d4b\u8bd5\u7236\u8282\u70b9<\/span>
\n println!<\/span>(<\/span>"child1 \u7684\u7236\u8282\u70b9: {:?}"<\/span>,<\/span> TreeNode<\/span>::<\/span>get_parent_value<\/span>(<\/span>&<\/span>child1)<\/span>)<\/span>;<\/span>
\n \/\/ \u671f\u671b: Some("\u6839")<\/span>
\n println!<\/span>(<\/span>"grandchild \u7684\u7236\u8282\u70b9: {:?}"<\/span>,<\/span> TreeNode<\/span>::<\/span>get_parent_value<\/span>(<\/span>&<\/span>grandchild)<\/span>)<\/span>;<\/span>
\n \/\/ \u671f\u671b: Some("\u5b501")<\/span>
\n println!<\/span>(<\/span>"root \u7684\u7236\u8282\u70b9: {:?}"<\/span>,<\/span> TreeNode<\/span>::<\/span>get_parent_value<\/span>(<\/span>&<\/span>root)<\/span>)<\/span>;<\/span>
\n \/\/ \u671f\u671b: None<\/span><\/p>\n

\/\/ \u6d4b\u8bd5\u627e\u6839\u8282\u70b9<\/span>
\n let<\/span> found_root =<\/span> TreeNode<\/span>::<\/span>get_root<\/span>(<\/span>&<\/span>grandchild)<\/span>;<\/span>
\n println!<\/span>(<\/span>"grandchild \u7684\u6839: {:?}"<\/span>,<\/span> found_root)<\/span>;<\/span>
\n \/\/ \u671f\u671b: TreeNode(\u6839)<\/span>
\n}<\/span><\/p>\n

\u671f\u671b\u8f93\u51fa：
\n\u5f85\u5b8c\u6210: 4
\n\u5df2\u5b8c\u6210: 0
\n\u5f85\u5b8c\u6210: 2
\n\u5df2\u5b8c\u6210: 2
\nhost: Some(\u201clocalhost\u201d)
\nport: Some(\u201c5432\u201d)
\nmissing: None
\nconfig \u8bbf\u95ee\u6b21\u6570: 2
\nconfig2 \u8bbf\u95ee\u6b21\u6570: 0
\nchild1 \u7684\u7236\u8282\u70b9: Some(\u201c\u6839\u201d)
\ngrandchild \u7684\u7236\u8282\u70b9: Some(\u201c\u5b501\u201d)
\nroot \u7684\u7236\u8282\u70b9: None
\ngrandchild \u7684\u6839: TreeNode(\u6839)<\/p>\n

\u5199\u597d\u4e86\u8d34\u8fc7\u6765，\u6ca1\u95ee\u9898\u5c31\u8fdb\u5165\u7b2c30\u8bfe：\u5b8f Macros \u5165\u95e8 👋<\/p>\n

\u8d34\u4ee3\u7801<\/h2>\n

\u5b8c\u6574\u53c2\u8003\u7b54\u6848（Rc \/ RefCell \/ Cell \/ Weak \u5185\u90e8\u53ef\u53d8\u6027\u7ecf\u5178\u7ec3\u4e60\u9898）<\/p>\n

use<\/span> std::<\/span>rc::<\/span><\/span>Rc<\/span>;<\/span>
\nuse<\/span> std::<\/span>cell::<\/span><\/span>RefCell<\/span>;<\/span>
\nuse<\/span> std::<\/span>cell::<\/span><\/span>Cell<\/span>;<\/span>
\nuse<\/span> std::<\/span>collections::<\/span><\/span>HashMap<\/span>;<\/span>
\nuse<\/span> std::<\/span>rc::<\/span><\/span>Weak<\/span>;<\/span><\/p>\n

\/\/ === \u9898\u76ee1：\u4efb\u52a1\u7ba1\u7406\u5668 ===<\/span>
\nstruct<\/span> TaskManager<\/span> {<\/span>
\n tasks:<\/span> RefCell<\/span><<\/span>Vec<\/span><<\/span>String<\/span>>><\/span>,<\/span>
\n completed_count:<\/span> Cell<\/span><<\/span>u32<\/span>><\/span>,<\/span>
\n}<\/span><\/p>\n

impl<\/span> TaskManager<\/span> {<\/span>
\n fn<\/span> new<\/span>(<\/span>)<\/span> -><\/span> Self<\/span> {<\/span>
\n TaskManager<\/span> {<\/span>
\n tasks:<\/span> RefCell<\/span>::<\/span>new<\/span>(<\/span>Vec<\/span>::<\/span>new<\/span>(<\/span>)<\/span>)<\/span>,<\/span>
\n completed_count:<\/span> Cell<\/span>::<\/span>new<\/span>(<\/span>0<\/span>)<\/span>,<\/span>
\n }<\/span>
\n }<\/span><\/p>\n

fn<\/span> add_task<\/span>(<\/span>&<\/span>self<\/span>,<\/span> task:<\/span> &<\/span>str<\/span>)<\/span> {<\/span>
\n self<\/span>.<\/span>tasks.<\/span>borrow_mut<\/span>(<\/span>)<\/span>.<\/span>push<\/span>(<\/span>task.<\/span>to_string<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n }<\/span><\/p>\n

fn<\/span> complete_task<\/span>(<\/span>&<\/span>self<\/span>,<\/span> index:<\/span> usize<\/span>)<\/span> -><\/span> bool<\/span> {<\/span>
\n let<\/span> mut<\/span> tasks =<\/span> self<\/span>.<\/span>tasks.<\/span>borrow_mut<\/span>(<\/span>)<\/span>;<\/span>
\n if<\/span> index >=<\/span> tasks.<\/span>len<\/span>(<\/span>)<\/span> {<\/span>
\n return<\/span> false<\/span>;<\/span>
\n }<\/span>
\n tasks.<\/span>remove<\/span>(<\/span>index)<\/span>;<\/span>
\n let<\/span> cnt =<\/span> self<\/span>.<\/span>completed_count.<\/span>get<\/span>(<\/span>)<\/span>;<\/span>
\n self<\/span>.<\/span>completed_count.<\/span>set<\/span>(<\/span>cnt +<\/span> 1<\/span>)<\/span>;<\/span>
\n true<\/span>
\n }<\/span><\/p>\n

fn<\/span> pending_count<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> usize<\/span> {<\/span>
\n self<\/span>.<\/span>tasks.<\/span>borrow<\/span>(<\/span>)<\/span>.<\/span>len<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> total_completed<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> u32<\/span> {<\/span>
\n self<\/span>.<\/span>completed_count.<\/span>get<\/span>(<\/span>)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

\/\/ === \u9898\u76ee2：\u5171\u4eab\u914d\u7f6e + \u7edf\u8ba1 ===<\/span>
\nstruct<\/span> SharedConfig<\/span> {<\/span>
\n data:<\/span> Rc<\/span><<\/span>HashMap<\/span><<\/span>String<\/span>,<\/span> String<\/span>>><\/span>,<\/span>
\n access_count:<\/span> Cell<\/span><<\/span>u64<\/span>><\/span>,<\/span>
\n}<\/span><\/p>\n

impl<\/span> SharedConfig<\/span> {<\/span>
\n fn<\/span> new<\/span>(<\/span>)<\/span> -><\/span> Self<\/span> {<\/span>
\n SharedConfig<\/span> {<\/span>
\n data:<\/span> Rc<\/span>::<\/span>new<\/span>(<\/span>HashMap<\/span>::<\/span>new<\/span>(<\/span>)<\/span>)<\/span>,<\/span>
\n access_count:<\/span> Cell<\/span>::<\/span>new<\/span>(<\/span>0<\/span>)<\/span>,<\/span>
\n }<\/span>
\n }<\/span><\/p>\n

fn<\/span> with_data<\/span>(<\/span>data:<\/span> HashMap<\/span><<\/span>String<\/span>,<\/span> String<\/span>><\/span>)<\/span> -><\/span> Self<\/span> {<\/span>
\n SharedConfig<\/span> {<\/span>
\n data:<\/span> Rc<\/span>::<\/span>new<\/span>(<\/span>data)<\/span>,<\/span>
\n access_count:<\/span> Cell<\/span>::<\/span>new<\/span>(<\/span>0<\/span>)<\/span>,<\/span>
\n }<\/span>
\n }<\/span><\/p>\n

fn<\/span> get<\/span>(<\/span>&<\/span>self<\/span>,<\/span> key:<\/span> &<\/span>str<\/span>)<\/span> -><\/span> Option<\/span><<\/span>String<\/span>><\/span> {<\/span>
\n \/\/ \u53ea\u8981\u8c03\u7528get\u5c31\u8ba1\u6570，\u4e0d\u7ba1key\u662f\u5426\u5b58\u5728，\u548c\u9898\u76ee\u793a\u4f8b\u8f93\u51fa\u4fdd\u6301\u4e00\u81f4<\/span>
\n let<\/span> current =<\/span> self<\/span>.<\/span>access_count.<\/span>get<\/span>(<\/span>)<\/span>;<\/span>
\n self<\/span>.<\/span>access_count.<\/span>set<\/span>(<\/span>current +<\/span> 1<\/span>)<\/span>;<\/span>
\n self<\/span>.<\/span>data.<\/span>get<\/span>(<\/span>key)<\/span>.<\/span>cloned<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> access_count<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> u64<\/span> {<\/span>
\n self<\/span>.<\/span>access_count.<\/span>get<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> clone_ref<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> Self<\/span> {<\/span>
\n SharedConfig<\/span> {<\/span>
\n data:<\/span> Rc<\/span>::<\/span>clone<\/span>(<\/span>&<\/span>self<\/span>.<\/span>data)<\/span>,<\/span>
\n access_count:<\/span> Cell<\/span>::<\/span>new<\/span>(<\/span>0<\/span>)<\/span>,<\/span>
\n }<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

\/\/ === \u9898\u76ee3：\u6811\u7ed3\u6784 + \u7236\u8282\u70b9\u5f31\u5f15\u7528 ===<\/span>
\nstruct<\/span> TreeNode<\/span> {<\/span>
\n value:<\/span> String<\/span>,<\/span>
\n children:<\/span> RefCell<\/span><<\/span>Vec<\/span><<\/span>Rc<\/span><<\/span>TreeNode<\/span>>><\/span>><\/span>,<\/span>
\n parent:<\/span> RefCell<\/span><<\/span>Option<\/span><<\/span>Weak<\/span><<\/span>TreeNode<\/span>>><\/span>><\/span>,<\/span>
\n}<\/span><\/p>\n

impl<\/span> TreeNode<\/span> {<\/span>
\n fn<\/span> new<\/span>(<\/span>value:<\/span> &<\/span>str<\/span>)<\/span> -><\/span> Rc<\/span><<\/span>Self<\/span>><\/span> {<\/span>
\n Rc<\/span>::<\/span>new<\/span>(<\/span>TreeNode<\/span> {<\/span>
\n value:<\/span> value.<\/span>to_string<\/span>(<\/span>)<\/span>,<\/span>
\n children:<\/span> RefCell<\/span>::<\/span>new<\/span>(<\/span>Vec<\/span>::<\/span>new<\/span>(<\/span>)<\/span>)<\/span>,<\/span>
\n parent:<\/span> RefCell<\/span>::<\/span>new<\/span>(<\/span>None<\/span>)<\/span>,<\/span>
\n }<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> add_child<\/span>(<\/span>parent:<\/span> &<\/span>Rc<\/span><<\/span>TreeNode<\/span>><\/span>,<\/span> child:<\/span> Rc<\/span><<\/span>TreeNode<\/span>><\/span>)<\/span> {<\/span>
\n \/\/ \u5b50\u8282\u70b9\u5b58\u5165\u7236\u8282\u70b9\u7684children\u5217\u8868<\/span>
\n parent.<\/span>children.<\/span>borrow_mut<\/span>(<\/span>)<\/span>.<\/span>push<\/span>(<\/span>child.<\/span>clone<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n \/\/ \u8bbe\u7f6e\u5b50\u8282\u70b9\u7684parent\u4e3a\u7236\u8282\u70b9\u7684\u5f31\u5f15\u7528，\u907f\u514d\u5faa\u73af\u5f15\u7528<\/span>
\n let<\/span> weak_parent =<\/span> Rc<\/span>::<\/span>downgrade<\/span>(<\/span>parent)<\/span>;<\/span>
\n *<\/span>child.<\/span>parent.<\/span>borrow_mut<\/span>(<\/span>)<\/span> =<\/span> Some<\/span>(<\/span>weak_parent)<\/span>;<\/span>
\n }<\/span><\/p>\n

fn<\/span> get_parent_value<\/span>(<\/span>node:<\/span> &<\/span>Rc<\/span><<\/span>TreeNode<\/span>><\/span>)<\/span> -><\/span> Option<\/span><<\/span>String<\/span>><\/span> {<\/span>
\n let<\/span> parent_opt =<\/span> node.<\/span>parent.<\/span>borrow<\/span>(<\/span>)<\/span>;<\/span>
\n match<\/span> &<\/span>*<\/span>parent_opt {<\/span>
\n Some<\/span>(<\/span>weak)<\/span> =><\/span> weak.<\/span>upgrade<\/span>(<\/span>)<\/span>.<\/span>map<\/span>(<\/span>|<\/span>p|<\/span><\/span> p.<\/span>value.<\/span>clone<\/span>(<\/span>)<\/span>)<\/span>,<\/span>
\n None<\/span> =><\/span> None<\/span>,<\/span>
\n }<\/span>
\n }<\/span><\/p>\n

fn<\/span> get_root<\/span>(<\/span>mut<\/span> node:<\/span> &<\/span>Rc<\/span><<\/span>TreeNode<\/span>><\/span>)<\/span> -><\/span> Rc<\/span><<\/span>TreeNode<\/span>><\/span> {<\/span>
\n loop<\/span> {<\/span>
\n let<\/span> parent_opt =<\/span> node.<\/span>parent.<\/span>borrow<\/span>(<\/span>)<\/span>;<\/span>
\n match<\/span> &<\/span>*<\/span>parent_opt {<\/span>
\n Some<\/span>(<\/span>weak)<\/span> =><\/span> {<\/span>
\n let<\/span> p =<\/span> weak.<\/span>upgrade<\/span>(<\/span>)<\/span>.<\/span>unwrap<\/span>(<\/span>)<\/span>;<\/span>
\n node =<\/span> &<\/span>p;<\/span>
\n }<\/span>
\n None<\/span> =><\/span> break<\/span>,<\/span>
\n }<\/span>
\n }<\/span>
\n node.<\/span>clone<\/span>(<\/span>)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

impl<\/span> std::<\/span>fmt::<\/span><\/span>Debug<\/span> for<\/span> TreeNode<\/span> {<\/span>
\n fn<\/span> fmt<\/span>(<\/span>&<\/span>self<\/span>,<\/span> f:<\/span> &<\/span>mut<\/span> std::<\/span>fmt::<\/span><\/span>Formatter<\/span><<\/span>'_<\/span>><\/span>)<\/span> -><\/span> std::<\/span>fmt::<\/span><\/span>Result<\/span> {<\/span>
\n write!<\/span>(<\/span>f,<\/span> "TreeNode({})"<\/span>,<\/span> self<\/span>.<\/span>value)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n \/\/ === \u6d4b\u8bd5 TaskManager ===<\/span>
\n let<\/span> tm =<\/span> TaskManager<\/span>::<\/span>new<\/span>(<\/span>)<\/span>;<\/span><\/p>\n

tm.<\/span>add_task<\/span>(<\/span>"\u5199\u62a5\u544a"<\/span>)<\/span>;<\/span>
\n tm.<\/span>add_task<\/span>(<\/span>"\u5f00\u4f1a"<\/span>)<\/span>;<\/span>
\n tm.<\/span>add_task<\/span>(<\/span>"\u4ee3\u7801\u5ba1\u67e5"<\/span>)<\/span>;<\/span>
\n tm.<\/span>add_task<\/span>(<\/span>"\u4feebug"<\/span>)<\/span>;<\/span><\/p>\n

println!<\/span>(<\/span>"\u5f85\u5b8c\u6210: {}"<\/span>,<\/span> tm.<\/span>pending_count<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u671f\u671b: 4<\/span>
\n println!<\/span>(<\/span>"\u5df2\u5b8c\u6210: {}"<\/span>,<\/span> tm.<\/span>total_completed<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u671f\u671b: 0<\/span><\/p>\n

assert!<\/span>(<\/span>tm.<\/span>complete_task<\/span>(<\/span>1<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u5b8c\u6210"\u5f00\u4f1a"<\/span>
\n assert!<\/span>(<\/span>tm.<\/span>complete_task<\/span>(<\/span>0<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u5b8c\u6210"\u5199\u62a5\u544a"（\u539findex 0，\u56e0\u4e3a"\u5f00\u4f1a"\u88ab\u79fb\u9664\u540e"\u5199\u62a5\u544a"\u53d8\u6210\u4e86index 0）<\/span>
\n assert!<\/span>(<\/span>!<\/span>tm.<\/span>complete_task<\/span>(<\/span>10<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u65e0\u6548\u7d22\u5f15<\/span><\/p>\n

println!<\/span>(<\/span>"\u5f85\u5b8c\u6210: {}"<\/span>,<\/span> tm.<\/span>pending_count<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u671f\u671b: 2<\/span>
\n println!<\/span>(<\/span>"\u5df2\u5b8c\u6210: {}"<\/span>,<\/span> tm.<\/span>total_completed<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u671f\u671b: 2<\/span><\/p>\n

\/\/ === \u6d4b\u8bd5 SharedConfig ===<\/span>
\n let<\/span> mut<\/span> data =<\/span> HashMap<\/span>::<\/span>new<\/span>(<\/span>)<\/span>;<\/span>
\n data.<\/span>insert<\/span>(<\/span>"host"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>,<\/span> "localhost"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n data.<\/span>insert<\/span>(<\/span>"port"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>,<\/span> "5432"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n data.<\/span>insert<\/span>(<\/span>"db"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>,<\/span> "mydb"<\/span>.<\/span>into<\/span>(<\/span>)<\/span>)<\/span>;<\/span><\/p>\n

let<\/span> config =<\/span> SharedConfig<\/span>::<\/span>with_data<\/span>(<\/span>data)<\/span>;<\/span>
\n let<\/span> config2 =<\/span> config.<\/span>clone_ref<\/span>(<\/span>)<\/span>;<\/span><\/p>\n

println!<\/span>(<\/span>"host: {:?}"<\/span>,<\/span> config.<\/span>get<\/span>(<\/span>"host"<\/span>)<\/span>)<\/span>;<\/span> \/\/ Some("localhost")<\/span>
\n println!<\/span>(<\/span>"port: {:?}"<\/span>,<\/span> config.<\/span>get<\/span>(<\/span>"port"<\/span>)<\/span>)<\/span>;<\/span> \/\/ Some("5432")<\/span>
\n println!<\/span>(<\/span>"missing: {:?}"<\/span>,<\/span> config.<\/span>get<\/span>(<\/span>"missing"<\/span>)<\/span>)<\/span>;<\/span> \/\/ None<\/span>
\n println!<\/span>(<\/span>"config \u8bbf\u95ee\u6b21\u6570: {}"<\/span>,<\/span> config.<\/span>access_count<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u671f\u671b: 3<\/span>
\n println!<\/span>(<\/span>"config2 \u8bbf\u95ee\u6b21\u6570: {}"<\/span>,<\/span> config2.<\/span>access_count<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u671f\u671b: 0（\u72ec\u7acb\u7684\u8ba1\u6570）<\/span><\/p>\n

\/\/ === \u6d4b\u8bd5 TreeNode ===<\/span>
\n let<\/span> root =<\/span> TreeNode<\/span>::<\/span>new<\/span>(<\/span>"\u6839"<\/span>)<\/span>;<\/span>
\n let<\/span> child1 =<\/span> TreeNode<\/span>::<\/span>new<\/span>(<\/span>"\u5b501"<\/span>)<\/span>;<\/span>
\n let<\/span> child2 =<\/span> TreeNode<\/span>::<\/span>new<\/span>(<\/span>"\u5b502"<\/span>)<\/span>;<\/span>
\n let<\/span> grandchild =<\/span> TreeNode<\/span>::<\/span>new<\/span>(<\/span>"\u5b591"<\/span>)<\/span>;<\/span><\/p>\n

TreeNode<\/span>::<\/span>add_child<\/span>(<\/span>&<\/span>root,<\/span> child1.<\/span>clone<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n TreeNode<\/span>::<\/span>add_child<\/span>(<\/span>&<\/span>root,<\/span> child2.<\/span>clone<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n TreeNode<\/span>::<\/span>add_child<\/span>(<\/span>&<\/span>child1,<\/span> grandchild.<\/span>clone<\/span>(<\/span>)<\/span>)<\/span>;<\/span><\/p>\n

\/\/ \u6d4b\u8bd5\u7236\u8282\u70b9<\/span>
\n println!<\/span>(<\/span>"child1 \u7684\u7236\u8282\u70b9: {:?}"<\/span>,<\/span> TreeNode<\/span>::<\/span>get_parent_value<\/span>(<\/span>&<\/span>child1)<\/span>)<\/span>;<\/span>
\n \/\/ \u671f\u671b: Some("\u6839")<\/span>
\n println!<\/span>(<\/span>"grandchild \u7684\u7236\u8282\u70b9: {:?}"<\/span>,<\/span> TreeNode<\/span>::<\/span>get_parent_value<\/span>(<\/span>&<\/span>grandchild)<\/span>)<\/span>;<\/span>
\n \/\/ \u671f\u671b: Some("\u5b501")<\/span>
\n println!<\/span>(<\/span>"root \u7684\u7236\u8282\u70b9: {:?}"<\/span>,<\/span> TreeNode<\/span>::<\/span>get_parent_value<\/span>(<\/span>&<\/span>root)<\/span>)<\/span>;<\/span>
\n \/\/ \u671f\u671b: None<\/span><\/p>\n

\/\/ \u6d4b\u8bd5\u627e\u6839\u8282\u70b9<\/span>
\n let<\/span> found_root =<\/span> TreeNode<\/span>::<\/span>get_root<\/span>(<\/span>&<\/span>grandchild)<\/span>;<\/span>
\n println!<\/span>(<\/span>"grandchild \u7684\u6839: {:?}"<\/span>,<\/span> found_root)<\/span>;<\/span>
\n \/\/ \u671f\u671b: TreeNode(\u6839)<\/span>
\n}<\/span><\/p>\n

\u8fd0\u884c\u8f93\u51fa\u8bf4\u660e<\/h3>\n

\u6ce8\u610f： config.get(\u201cmissing\u201d) \u8fd9\u4e00\u884c\u4e5f\u89e6\u53d1\u4e00\u6b21\u8bbf\u95ee\u8ba1\u6570，\u6700\u7ec8 config \u7684\u8bbf\u95ee\u6b21\u6570 =3\u3002<\/p>\n

plaintext<\/p>\n

\u5f85\u5b8c\u6210: 4
\n\u5df2\u5b8c\u6210: 0
\n\u5f85\u5b8c\u6210: 2
\n\u5df2\u5b8c\u6210: 2
\nhost: Some(\u201clocalhost\u201d)
\nport: Some(\u201c5432\u201d)
\nmissing: None
\nconfig \u8bbf\u95ee\u6b21\u6570: 3
\nconfig2 \u8bbf\u95ee\u6b21\u6570: 0
\nchild1 \u7684\u7236\u8282\u70b9: Some(\u201c\u6839\u201d)
\ngrandchild \u7684\u7236\u8282\u70b9: Some(\u201c\u5b501\u201d)
\nroot \u7684\u7236\u8282\u70b9: None
\ngrandchild \u7684\u6839: TreeNode(\u6839)<\/p>\n

\u6838\u5fc3\u77e5\u8bc6\u70b9\u8be6\u89e3（Rc\u2011RefCell\u2011Cell\u2011Weak）<\/h2>\n

1. TaskManager（\u5185\u90e8\u53ef\u53d8\u6027）<\/h3>\n