{"id":102564,"date":"2026-09-09T07:57:18","date_gmt":"2026-09-08T23:57:18","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/102564.html"},"modified":"2026-09-09T07:57:18","modified_gmt":"2026-09-08T23:57:18","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%ac24%e8%af%be%ef%bc%9atrait-%e5%9f%ba%e7%a1%80","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/102564.html","title":{"rendered":"\u3010Rust\u5165\u95e8\u77e5\u8bc6\u70b9\u5b66\u4e0e\u7ec3\u3011\u7b2c24\u8bfe\uff1aTrait \u57fa\u7840"},"content":{"rendered":"

\u77e5\u8bc6\u70b9：\u5b9a\u4e49\u548c\u5b9e\u73b0 Trait<\/h2>\n

Trait \u5b9a\u4e49\u4e86\u4e00\u7ec4\u884c\u4e3a（\u65b9\u6cd5），\u7c7b\u578b\u53ef\u4ee5\u5b9e\u73b0\u8fd9\u4e9b\u884c\u4e3a：<\/p>\n

\/\/ \u5b9a\u4e49 trait<\/span>
\ntrait<\/span> Speak<\/span> {<\/span>
\n fn<\/span> speak<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> String<\/span>;<\/span> \/\/ \u5fc5\u987b\u5b9e\u73b0\u7684\u65b9\u6cd5<\/span>
\n fn<\/span> greet<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> String<\/span> {<\/span> \/\/ \u5e26\u9ed8\u8ba4\u5b9e\u73b0\u7684\u65b9\u6cd5<\/span>
\n format!<\/span>(<\/span>"\u4f60\u597d！"<\/span>)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

\/\/ \u4e3a\u4e0d\u540c\u7c7b\u578b\u5b9e\u73b0 trait<\/span>
\nstruct<\/span> Dog<\/span> {<\/span>
\n name:<\/span> String<\/span>,<\/span>
\n}<\/span><\/p>\n

struct<\/span> Cat<\/span> {<\/span>
\n name:<\/span> String<\/span>,<\/span>
\n}<\/span><\/p>\n

impl<\/span> Speak<\/span> for<\/span> Dog<\/span> {<\/span>
\n fn<\/span> speak<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> String<\/span> {<\/span>
\n format!<\/span>(<\/span>"{}\u8bf4：\u6c6a\u6c6a！"<\/span>,<\/span> self<\/span>.<\/span>name)<\/span>
\n }<\/span>
\n \/\/ greet \u4f7f\u7528\u9ed8\u8ba4\u5b9e\u73b0<\/span>
\n}<\/span><\/p>\n

impl<\/span> Speak<\/span> for<\/span> Cat<\/span> {<\/span>
\n fn<\/span> speak<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> String<\/span> {<\/span>
\n format!<\/span>(<\/span>"{}\u8bf4：\u55b5~"<\/span>,<\/span> self<\/span>.<\/span>name)<\/span>
\n }<\/span><\/p>\n

\/\/ \u8986\u76d6\u9ed8\u8ba4\u5b9e\u73b0<\/span>
\n fn<\/span> greet<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> String<\/span> {<\/span>
\n format!<\/span>(<\/span>"{}\u61d2\u6d0b\u6d0b\u5730\u770b\u4e86\u4f60\u4e00\u773c"<\/span>,<\/span> self<\/span>.<\/span>name)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> dog =<\/span> Dog<\/span> {<\/span> name:<\/span> String<\/span>::<\/span>from<\/span>(<\/span>"\u65fa\u8d22"<\/span>)<\/span> }<\/span>;<\/span>
\n let<\/span> cat =<\/span> Cat<\/span> {<\/span> name:<\/span> String<\/span>::<\/span>from<\/span>(<\/span>"\u54aa\u54aa"<\/span>)<\/span> }<\/span>;<\/span><\/p>\n

println!<\/span>(<\/span>"{}"<\/span>,<\/span> dog.<\/span>speak<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u65fa\u8d22\u8bf4：\u6c6a\u6c6a！<\/span>
\n println!<\/span>(<\/span>"{}"<\/span>,<\/span> dog.<\/span>greet<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u4f60\u597d！<\/span>
\n println!<\/span>(<\/span>"{}"<\/span>,<\/span> cat.<\/span>speak<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u54aa\u54aa\u8bf4：\u55b5~<\/span>
\n println!<\/span>(<\/span>"{}"<\/span>,<\/span> cat.<\/span>greet<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ \u54aa\u54aa\u61d2\u6d0b\u6d0b\u5730\u770b\u4e86\u4f60\u4e00\u773c<\/span>
\n}<\/span><\/p>\n

\u77e5\u8bc6\u70b9：\u6d3e\u751f\u5b8f（derive）<\/h2>\n

\u6807\u51c6\u5e93\u63d0\u4f9b\u4e86\u5f88\u591a\u53ef\u4ee5\u81ea\u52a8\u5b9e\u73b0\u7684 trait：<\/p>\n

\/\/ #[derive(…)] \u81ea\u52a8\u5b9e\u73b0\u5e38\u89c1 trait<\/span>
\n#[derive(Debug, Clone, PartialEq)]<\/span>
\nstruct<\/span> Point<\/span> {<\/span>
\n x:<\/span> f64<\/span>,<\/span>
\n y:<\/span> f64<\/span>,<\/span>
\n}<\/span><\/p>\n

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]<\/span>
\nstruct<\/span> Color<\/span> {<\/span>
\n r:<\/span> u8<\/span>,<\/span>
\n g:<\/span> u8<\/span>,<\/span>
\n b:<\/span> u8<\/span>,<\/span>
\n}<\/span><\/p>\n

\/\/ \u5e38\u7528\u53ef\u6d3e\u751f\u7684 trait：<\/span>
\n\/\/ Debug \u2014 {:?} \u683c\u5f0f\u5316<\/span>
\n\/\/ Clone \u2014 .clone() \u6df1\u62f7\u8d1d<\/span>
\n\/\/ Copy \u2014 \u81ea\u52a8\u6309\u4f4d\u590d\u5236（\u4e0d\u80fd\u548c Drop \u5171\u5b58）<\/span>
\n\/\/ PartialEq \u2014 == \u548c !=<\/span>
\n\/\/ Eq \u2014 \u5b8c\u5168\u7b49\u4ef7\u5173\u7cfb（\u8981\u6c42 PartialEq）<\/span>
\n\/\/ PartialOrd \u2014 < > <= >=<\/span>
\n\/\/ Ord \u2014 \u5168\u5e8f\u5173\u7cfb<\/span>
\n\/\/ Hash \u2014 \u53ef\u4f5c\u4e3a HashMap \u7684\u952e<\/span>
\n\/\/ Default \u2014 \u9ed8\u8ba4\u503c<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> p1 =<\/span> Point<\/span> {<\/span> x:<\/span> 1.0<\/span>,<\/span> y:<\/span> 2.0<\/span> }<\/span>;<\/span>
\n let<\/span> p2 =<\/span> p1.<\/span>clone<\/span>(<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"p1: {:?}"<\/span>,<\/span> p1)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u76f8\u7b49? {}"<\/span>,<\/span> p1 ==<\/span> p2)<\/span>;<\/span><\/p>\n

let<\/span> red =<\/span> Color<\/span> {<\/span> r:<\/span> 255<\/span>,<\/span> g:<\/span> 0<\/span>,<\/span> b:<\/span> 0<\/span> }<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u989c\u8272: {:?}"<\/span>,<\/span> red)<\/span>;<\/span><\/p>\n

\/\/ Default trait<\/span>
\n let<\/span> default_point =<\/span> Point<\/span> {<\/span> x:<\/span> 0.0<\/span>,<\/span> y:<\/span> 0.0<\/span> }<\/span>;<\/span>
\n \/\/ \u4e5f\u53ef\u4ee5\u624b\u52a8\u5b9e\u73b0 Default<\/span>
\n}<\/span><\/p>\n

\/\/ \u624b\u52a8\u5b9e\u73b0 Default<\/span>
\nimpl<\/span> Default<\/span> for<\/span> Point<\/span> {<\/span>
\n fn<\/span> default<\/span>(<\/span>)<\/span> -><\/span> Self<\/span> {<\/span>
\n Point<\/span> {<\/span> x:<\/span> 0.0<\/span>,<\/span> y:<\/span> 0.0<\/span> }<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

\u77e5\u8bc6\u70b9：Trait \u4f5c\u4e3a\u53c2\u6570<\/h2>\n

trait<\/span> Area<\/span> {<\/span>
\n fn<\/span> area<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> f64<\/span>;<\/span>
\n}<\/span><\/p>\n

struct<\/span> Circle<\/span> {<\/span> radius:<\/span> f64<\/span> }<\/span>
\nstruct<\/span> Rectangle<\/span> {<\/span> width:<\/span> f64<\/span>,<\/span> height:<\/span> f64<\/span> }<\/span><\/p>\n

impl<\/span> Area<\/span> for<\/span> Circle<\/span> {<\/span>
\n fn<\/span> area<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> f64<\/span> {<\/span>
\n std::<\/span><\/span>f64<\/span>::<\/span>consts::<\/span><\/span>PI<\/span> *<\/span> self<\/span>.<\/span>radius *<\/span> self<\/span>.<\/span>radius
\n }<\/span>
\n}<\/span><\/p>\n

impl<\/span> Area<\/span> for<\/span> Rectangle<\/span> {<\/span>
\n fn<\/span> area<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> f64<\/span> {<\/span>
\n self<\/span>.<\/span>width *<\/span> self<\/span>.<\/span>height
\n }<\/span>
\n}<\/span><\/p>\n

\/\/ \u65b9\u5f0f1：impl Trait \u8bed\u6cd5（\u7b80\u6d01）<\/span>
\nfn<\/span> print_area<\/span>(<\/span>shape:<\/span> &<\/span>impl<\/span> Area<\/span>)<\/span> {<\/span>
\n println!<\/span>(<\/span>"\u9762\u79ef: {:.2}"<\/span>,<\/span> shape.<\/span>area<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

\/\/ \u65b9\u5f0f2：\u6cdb\u578b + trait bound（\u66f4\u7075\u6d3b）<\/span>
\nfn<\/span> print_area2<\/span><<\/span>T<\/span>:<\/span> Area<\/span>><\/span>(<\/span>shape:<\/span> &<\/span>T<\/span>)<\/span> {<\/span>
\n println!<\/span>(<\/span>"\u9762\u79ef: {:.2}"<\/span>,<\/span> shape.<\/span>area<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

\/\/ \u65b9\u5f0f3：where \u5b50\u53e5（\u591a\u4e2a bound \u65f6\u66f4\u6e05\u6670）<\/span>
\nfn<\/span> compare_areas<\/span><<\/span>T<\/span>:<\/span> Area<\/span> +<\/span> std::<\/span>fmt::<\/span><\/span>Debug<\/span>><\/span>(<\/span>a:<\/span> &<\/span>T<\/span>,<\/span> b:<\/span> &<\/span>T<\/span>)<\/span> {<\/span>
\n let<\/span> area_a =<\/span> a.<\/span>area<\/span>(<\/span>)<\/span>;<\/span>
\n let<\/span> area_b =<\/span> b.<\/span>area<\/span>(<\/span>)<\/span>;<\/span>
\n if<\/span> area_a ><\/span> area_b {<\/span>
\n println!<\/span>(<\/span>"{:?} \u66f4\u5927"<\/span>,<\/span> a)<\/span>;<\/span>
\n }<\/span> else<\/span> {<\/span>
\n println!<\/span>(<\/span>"{:?} \u66f4\u5927"<\/span>,<\/span> b)<\/span>;<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

\/\/ \u8fd4\u56de trait \u5bf9\u8c61（\u52a8\u6001\u5206\u53d1）<\/span>
\nfn<\/span> create_shape<\/span>(<\/span>kind:<\/span> &<\/span>str<\/span>)<\/span> -><\/span> Box<\/span><<\/span>dyn<\/span> Area<\/span>><\/span> {<\/span>
\n match<\/span> kind {<\/span>
\n "circle"<\/span> =><\/span> Box<\/span>::<\/span>new<\/span>(<\/span>Circle<\/span> {<\/span> radius:<\/span> 5.0<\/span> }<\/span>)<\/span>,<\/span>
\n "rectangle"<\/span> =><\/span> Box<\/span>::<\/span>new<\/span>(<\/span>Rectangle<\/span> {<\/span> width:<\/span> 3.0<\/span>,<\/span> height:<\/span> 4.0<\/span> }<\/span>)<\/span>,<\/span>
\n _ =><\/span> panic!<\/span>(<\/span>"\u672a\u77e5\u5f62\u72b6"<\/span>)<\/span>,<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> circle =<\/span> Circle<\/span> {<\/span> radius:<\/span> 3.0<\/span> }<\/span>;<\/span>
\n let<\/span> rect =<\/span> Rectangle<\/span> {<\/span> width:<\/span> 4.0<\/span>,<\/span> height:<\/span> 5.0<\/span> }<\/span>;<\/span><\/p>\n

print_area<\/span>(<\/span>&<\/span>circle)<\/span>;<\/span> \/\/ \u9762\u79ef: 28.27<\/span>
\n print_area<\/span>(<\/span>&<\/span>rect)<\/span>;<\/span> \/\/ \u9762\u79ef: 20.00<\/span><\/p>\n

\/\/ \u52a8\u6001\u5206\u53d1<\/span>
\n let<\/span> shape =<\/span> create_shape<\/span>(<\/span>"circle"<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u52a8\u6001\u9762\u79ef: {:.2}"<\/span>,<\/span> shape.<\/span>area<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

\u77e5\u8bc6\u70b9：\u591a\u4e2a Trait Bound<\/h2>\n

use<\/span> std::<\/span><\/span>fmt;<\/span><\/p>\n

trait<\/span> Drawable<\/span> {<\/span>
\n fn<\/span> draw<\/span>(<\/span>&<\/span>self<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

trait<\/span> Resizable<\/span> {<\/span>
\n fn<\/span> resize<\/span>(<\/span>&<\/span>mut<\/span> self<\/span>,<\/span> factor:<\/span> f64<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

#[derive(Debug)]<\/span>
\nstruct<\/span> Box<\/span> {<\/span>
\n size:<\/span> f64<\/span>,<\/span>
\n}<\/span><\/p>\n

impl<\/span> Drawable<\/span> for<\/span> Box<\/span> {<\/span>
\n fn<\/span> draw<\/span>(<\/span>&<\/span>self<\/span>)<\/span> {<\/span>
\n println!<\/span>(<\/span>"\u7ed8\u5236\u5927\u5c0f\u4e3a {} \u7684\u76d2\u5b50"<\/span>,<\/span> self<\/span>.<\/span>size)<\/span>;<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

impl<\/span> Resizable<\/span> for<\/span> Box<\/span> {<\/span>
\n fn<\/span> resize<\/span>(<\/span>&<\/span>mut<\/span> self<\/span>,<\/span> factor:<\/span> f64<\/span>)<\/span> {<\/span>
\n self<\/span>.<\/span>size *=<\/span> factor;<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

impl<\/span> fmt::<\/span><\/span>Display<\/span> for<\/span> Box<\/span> {<\/span>
\n fn<\/span> fmt<\/span>(<\/span>&<\/span>self<\/span>,<\/span> f:<\/span> &<\/span>mut<\/span> fmt::<\/span><\/span>Formatter<\/span><<\/span>'_<\/span>><\/span>)<\/span> -><\/span> fmt::<\/span><\/span>Result<\/span> {<\/span>
\n write!<\/span>(<\/span>f,<\/span> "Box(size={})"<\/span>,<\/span> self<\/span>.<\/span>size)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

\/\/ \u8981\u6c42\u540c\u65f6\u5b9e\u73b0\u591a\u4e2a trait<\/span>
\nfn<\/span> process<\/span><<\/span>T<\/span>:<\/span> Drawable<\/span> +<\/span> Resizable<\/span> +<\/span> fmt::<\/span><\/span>Display<\/span>><\/span>(<\/span>item:<\/span> &<\/span>mut<\/span> T<\/span>)<\/span> {<\/span>
\n println!<\/span>(<\/span>"\u5904\u7406\u524d: {}"<\/span>,<\/span> item)<\/span>;<\/span>
\n item.<\/span>draw<\/span>(<\/span>)<\/span>;<\/span>
\n item.<\/span>resize<\/span>(<\/span>2.0<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u5904\u7406\u540e: {}"<\/span>,<\/span> item)<\/span>;<\/span>
\n item.<\/span>draw<\/span>(<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

\/\/ where \u5b50\u53e5\u5199\u6cd5（\u66f4\u6e05\u6670）<\/span>
\nfn<\/span> process2<\/span><<\/span>T<\/span>><\/span>(<\/span>item:<\/span> &<\/span>mut<\/span> T<\/span>)<\/span>
\nwhere<\/span>
\n T<\/span>:<\/span> Drawable<\/span> +<\/span> Resizable<\/span> +<\/span> fmt::<\/span><\/span>Display<\/span>,<\/span>
\n{<\/span>
\n println!<\/span>(<\/span>"\u5904\u7406\u524d: {}"<\/span>,<\/span> item)<\/span>;<\/span>
\n item.<\/span>resize<\/span>(<\/span>0.5<\/span>)<\/span>;<\/span>
\n item.<\/span>draw<\/span>(<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> mut<\/span> b =<\/span> Box<\/span> {<\/span> size:<\/span> 10.0<\/span> }<\/span>;<\/span>
\n process<\/span>(<\/span>&<\/span>mut<\/span> b)<\/span>;<\/span>
\n}<\/span><\/p>\n

\u77e5\u8bc6\u70b9：trait \u5bf9\u8c61\u4e0e dyn<\/h2>\n

use<\/span> std::<\/span><\/span>fmt;<\/span><\/p>\n

trait<\/span> Animal<\/span>:<\/span> fmt::<\/span><\/span>Display<\/span> {<\/span>
\n fn<\/span> name<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> &<\/span>str<\/span>;<\/span>
\n fn<\/span> sound<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> &<\/span>str<\/span>;<\/span>
\n}<\/span><\/p>\n

struct<\/span> Cow<\/span>;<\/span>
\nstruct<\/span> Sheep<\/span>;<\/span><\/p>\n

impl<\/span> fmt::<\/span><\/span>Display<\/span> for<\/span> Cow<\/span> {<\/span>
\n fn<\/span> fmt<\/span>(<\/span>&<\/span>self<\/span>,<\/span> f:<\/span> &<\/span>mut<\/span> fmt::<\/span><\/span>Formatter<\/span><<\/span>'_<\/span>><\/span>)<\/span> -><\/span> fmt::<\/span><\/span>Result<\/span> {<\/span>
\n write!<\/span>(<\/span>f,<\/span> "\u725b"<\/span>)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

impl<\/span> fmt::<\/span><\/span>Display<\/span> for<\/span> Sheep<\/span> {<\/span>
\n fn<\/span> fmt<\/span>(<\/span>&<\/span>self<\/span>,<\/span> f:<\/span> &<\/span>mut<\/span> fmt::<\/span><\/span>Formatter<\/span><<\/span>'_<\/span>><\/span>)<\/span> -><\/span> fmt::<\/span><\/span>Result<\/span> {<\/span>
\n write!<\/span>(<\/span>f,<\/span> "\u7f8a"<\/span>)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

impl<\/span> Animal<\/span> for<\/span> Cow<\/span> {<\/span>
\n fn<\/span> name<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> &<\/span>str<\/span> {<\/span> "\u725b"<\/span> }<\/span>
\n fn<\/span> sound<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> &<\/span>str<\/span> {<\/span> "\u54de~"<\/span> }<\/span>
\n}<\/span><\/p>\n

impl<\/span> Animal<\/span> for<\/span> Sheep<\/span> {<\/span>
\n fn<\/span> name<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> &<\/span>str<\/span> {<\/span> "\u7f8a"<\/span> }<\/span>
\n fn<\/span> sound<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> &<\/span>str<\/span> {<\/span> "\u54a9~"<\/span> }<\/span>
\n}<\/span><\/p>\n

\/\/ \u7528 Box<dyn Trait> \u5b58\u50a8\u4e0d\u540c\u7c7b\u578b\u7684 trait \u5b9e\u73b0<\/span>
\nfn<\/span> make_noise<\/span>(<\/span>animal:<\/span> &<\/span>dyn<\/span> Animal<\/span>)<\/span> {<\/span>
\n println!<\/span>(<\/span>"{}\u8bf4：{}"<\/span>,<\/span> animal.<\/span>name<\/span>(<\/span>)<\/span>,<\/span> animal.<\/span>sound<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> animals:<\/span> Vec<\/span><<\/span>Box<\/span><<\/span>dyn<\/span> Animal<\/span>>><\/span> =<\/span> vec!<\/span>[<\/span>
\n Box<\/span>::<\/span>new<\/span>(<\/span>Cow<\/span>)<\/span>,<\/span>
\n Box<\/span>::<\/span>new<\/span>(<\/span>Sheep<\/span>)<\/span>,<\/span>
\n Box<\/span>::<\/span>new<\/span>(<\/span>Cow<\/span>)<\/span>,<\/span>
\n ]<\/span>;<\/span><\/p>\n

\/\/ \u52a8\u6001\u5206\u53d1：\u904d\u5386\u4e0d\u540c\u7c7b\u578b\u7684\u52a8\u7269<\/span>
\n for<\/span> animal in<\/span> &<\/span>animals {<\/span>
\n make_noise<\/span>(<\/span>animal.<\/span>as_ref<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n }<\/span><\/p>\n

\/\/ \u4e5f\u53ef\u4ee5\u7528 &dyn Trait<\/span>
\n let<\/span> cow =<\/span> Cow<\/span>;<\/span>
\n make_noise<\/span>(<\/span>&<\/span>cow)<\/span>;<\/span>
\n}<\/span><\/p>\n

\u77e5\u8bc6\u70b9：\u4e3a\u6cdb\u578b\u7c7b\u578b\u5b9e\u73b0 Trait<\/h2>\n

use<\/span> std::<\/span><\/span>fmt;<\/span><\/p>\n

\/\/ \u6cdb\u578b\u7ed3\u6784\u4f53<\/span>
\n#[derive(Debug)]<\/span>
\nstruct<\/span> Wrapper<\/span><<\/span>T<\/span>><\/span> {<\/span>
\n value:<\/span> T<\/span>,<\/span>
\n}<\/span><\/p>\n

\/\/ \u4e3a\u6cdb\u578b\u7c7b\u578b\u5b9e\u73b0 trait<\/span>
\nimpl<\/span><<\/span>T<\/span>:<\/span> fmt::<\/span><\/span>Display<\/span>><\/span> fmt::<\/span><\/span>Display<\/span> for<\/span> Wrapper<\/span><<\/span>T<\/span>><\/span> {<\/span>
\n fn<\/span> fmt<\/span>(<\/span>&<\/span>self<\/span>,<\/span> f:<\/span> &<\/span>mut<\/span> fmt::<\/span><\/span>Formatter<\/span><<\/span>'_<\/span>><\/span>)<\/span> -><\/span> fmt::<\/span><\/span>Result<\/span> {<\/span>
\n write!<\/span>(<\/span>f,<\/span> "[{}]"<\/span>,<\/span> self<\/span>.<\/span>value)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

\/\/ \u4e3a\u6cdb\u578b\u7c7b\u578b\u5b9e\u73b0\u81ea\u5b9a\u4e49 trait<\/span>
\ntrait<\/span> Unwrap<\/span> {<\/span>
\n type<\/span> Inner<\/span>;<\/span>
\n fn<\/span> unwrap_value<\/span>(<\/span>self<\/span>)<\/span> -><\/span> Self<\/span>::<\/span>Inner<\/span>;<\/span>
\n}<\/span><\/p>\n

impl<\/span><<\/span>T<\/span>><\/span> Unwrap<\/span> for<\/span> Wrapper<\/span><<\/span>T<\/span>><\/span> {<\/span>
\n type<\/span> Inner<\/span> =<\/span> T<\/span>;<\/span>
\n fn<\/span> unwrap_value<\/span>(<\/span>self<\/span>)<\/span> -><\/span> T<\/span> {<\/span>
\n self<\/span>.<\/span>value
\n }<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n let<\/span> w =<\/span> Wrapper<\/span> {<\/span> value:<\/span> 42<\/span> }<\/span>;<\/span>
\n println!<\/span>(<\/span>"{}"<\/span>,<\/span> w)<\/span>;<\/span> \/\/ [42]<\/span><\/p>\n

let<\/span> w2 =<\/span> Wrapper<\/span> {<\/span> value:<\/span> String<\/span>::<\/span>from<\/span>(<\/span>"hello"<\/span>)<\/span> }<\/span>;<\/span>
\n println!<\/span>(<\/span>"{}"<\/span>,<\/span> w2)<\/span>;<\/span> \/\/ [hello]<\/span><\/p>\n

let<\/span> val =<\/span> w2.<\/span>unwrap_value<\/span>(<\/span>)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u89e3\u5305: {}"<\/span>,<\/span> val)<\/span>;<\/span>
\n}<\/span><\/p>\n

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

\u6982\u5ff5 \u5199\u6cd5
\n\u5b9a\u4e49 trait trait Name { fn method(&self); }
\n\u5b9e\u73b0 trait impl Name for Type { \u2026 }
\n\u9ed8\u8ba4\u65b9\u6cd5 fn method(&self) -> T { \u2026 }
\n\u6d3e\u751f\u5b8f #[derive(Debug, Clone, PartialEq)]
\nimpl Trait \u53c2\u6570 fn foo(x: &impl Trait)
\n\u6cdb\u578b + bound fn foo<T: Trait>(x: &T)
\nwhere \u5b50\u53e5 fn foo(x: &T) where T: Trait
\n\u591a\u4e2a bound T: Trait1 + Trait2
\ntrait \u5bf9\u8c61 Box \/ &dyn Trait
\n\u8fd4\u56de trait \u5bf9\u8c61 -> Box<\/p>\n

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

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

use<\/span> std::<\/span><\/span>fmt;<\/span><\/p>\n

\/\/ \u8865\u5168：\u5b9a\u4e49\u4e00\u4e2a trait Shape，\u5305\u542b\u4ee5\u4e0b\u65b9\u6cd5：<\/span>
\n\/\/ 1. area(&self) -> f64 \u8ba1\u7b97\u9762\u79ef<\/span>
\n\/\/ 2. perimeter(&self) -> f64 \u8ba1\u7b97\u5468\u957f<\/span>
\n\/\/ 3. describe(&self) -> String \u8fd4\u56de\u63cf\u8ff0（\u6709\u9ed8\u8ba4\u5b9e\u73b0）<\/span>
\n\/\/ \u9ed8\u8ba4\u5b9e\u73b0\u8fd4\u56de\u683c\u5f0f: "\u9762\u79ef={:.2}, \u5468\u957f={:.2}"<\/span><\/p>\n

\/\/ \u8865\u5168：\u5b9a\u4e49\u7ed3\u6784\u4f53 Triangle，\u5b57\u6bb5\u4e3a a, b, c（\u4e09\u8fb9\u957f\u5ea6，f64）<\/span><\/p>\n

\/\/ \u8865\u5168：\u4e3a Triangle \u5b9e\u73b0 Shape trait<\/span>
\n\/\/ \u9762\u79ef\u7528\u6d77\u4f26\u516c\u5f0f：s = (a+b+c)\/2, area = sqrt(s*(s-a)*(s-b)*(s-c))<\/span>
\n\/\/ \u5468\u957f = a + b + c<\/span><\/p>\n

\/\/ \u8865\u5168：\u4e3a Triangle \u5b9e\u73b0 Display trait<\/span>
\n\/\/ \u683c\u5f0f: "\u4e09\u89d2\u5f62({},{},{})", a, b, c<\/span><\/p>\n

\/\/ \u8865\u5168：\u5b9a\u4e49\u7ed3\u6784\u4f53 RegularPolygon（\u6b63\u591a\u8fb9\u5f62）<\/span>
\n\/\/ \u5b57\u6bb5：sides: usize（\u8fb9\u6570）, side_length: f64（\u8fb9\u957f）<\/span><\/p>\n

\/\/ \u8865\u5168：\u4e3a RegularPolygon \u5b9e\u73b0 Shape trait<\/span>
\n\/\/ \u9762\u79ef = (n * s\u00b2) \/ (4 * tan(\u03c0\/n))<\/span>
\n\/\/ \u5468\u957f = n * s<\/span><\/p>\n

\/\/ \u8865\u5168：\u4e3a RegularPolygon \u5b9e\u73b0 Display trait<\/span>
\n\/\/ \u683c\u5f0f: "\u6b63{n}\u8fb9\u5f62(\u8fb9\u957f={})", sides, side_length<\/span><\/p>\n

\/\/ \u8865\u5168：\u5b9e\u73b0\u51fd\u6570 largest_shape<\/span>
\n\/\/ \u63a5\u53d7\u4e00\u4e2a &[Box<dyn Shape>]，\u8fd4\u56de\u9762\u79ef\u6700\u5927\u7684\u5f62\u72b6\u7684\u7d22\u5f15<\/span>
\nfn<\/span> largest_shape<\/span>(<\/span>shapes:<\/span> &<\/span>[<\/span>Box<\/span><<\/span>dyn<\/span> Shape<\/span>><\/span>]<\/span>)<\/span> -><\/span> usize<\/span> {<\/span>
\n \/\/ \u8865\u5168<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n}<\/span><\/p>\n

\/\/ \u8865\u5168：\u5b9e\u73b0\u51fd\u6570 total_area<\/span>
\n\/\/ \u63a5\u53d7\u4e00\u4e2a &[Box<dyn Shape>]，\u8fd4\u56de\u6240\u6709\u5f62\u72b6\u7684\u9762\u79ef\u4e4b\u548c<\/span>
\nfn<\/span> total_area<\/span>(<\/span>shapes:<\/span> &<\/span>[<\/span>Box<\/span><<\/span>dyn<\/span> Shape<\/span>><\/span>]<\/span>)<\/span> -><\/span> f64<\/span> {<\/span>
\n \/\/ \u8865\u5168<\/span>
\n todo!<\/span>(<\/span>)<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n \/\/ \u8865\u5168：\u521b\u5efa\u5f62\u72b6\u5217\u8868<\/span>
\n \/\/ 1. \u4e09\u89d2\u5f62 (3, 4, 5)<\/span>
\n \/\/ 2. \u6b63\u65b9\u5f62（\u6b634\u8fb9\u5f62，\u8fb9\u957f 5）<\/span>
\n \/\/ 3. \u6b63\u516d\u8fb9\u5f62（\u8fb9\u957f 3）<\/span>
\n \/\/ 4. \u4e09\u89d2\u5f62 (5, 12, 13)<\/span><\/p>\n

\/\/ \u8865\u5168：\u904d\u5386\u6253\u5370\u6bcf\u4e2a\u5f62\u72b6\u7684\u63cf\u8ff0<\/span>
\n \/\/ \u671f\u671b\u8f93\u51fa（\u6bcf\u884c\u4e00\u4e2a）:<\/span>
\n \/\/ \u4e09\u89d2\u5f62(3,4,5): \u9762\u79ef=6.00, \u5468\u957f=12.00<\/span>
\n \/\/ \u6b634\u8fb9\u5f62(\u8fb9\u957f=5): \u9762\u79ef=25.00, \u5468\u957f=20.00<\/span>
\n \/\/ \u6b636\u8fb9\u5f62(\u8fb9\u957f=3): \u9762\u79ef=23.38, \u5468\u957f=18.00<\/span>
\n \/\/ \u4e09\u89d2\u5f62(5,12,13): \u9762\u79ef=30.00, \u5468\u957f=30.00<\/span><\/p>\n

\/\/ \u8865\u5168：\u6253\u5370\u6700\u5927\u9762\u79ef\u7684\u7d22\u5f15<\/span>
\n \/\/ \u671f\u671b: \u6700\u5927\u9762\u79ef\u7d22\u5f15: 3<\/span><\/p>\n

\/\/ \u8865\u5168：\u6253\u5370\u603b\u9762\u79ef<\/span>
\n \/\/ \u671f\u671b: \u603b\u9762\u79ef: 84.38<\/span>
\n}<\/span><\/p>\n

\u671f\u671b\u8f93\u51fa：
\n\u4e09\u89d2\u5f62(3,4,5): \u9762\u79ef=6.00, \u5468\u957f=12.00
\n\u6b634\u8fb9\u5f62(\u8fb9\u957f=5): \u9762\u79ef=25.00, \u5468\u957f=20.00
\n\u6b636\u8fb9\u5f62(\u8fb9\u957f=3): \u9762\u79ef=23.38, \u5468\u957f=18.00
\n\u4e09\u89d2\u5f62(5,12,13): \u9762\u79ef=30.00, \u5468\u957f=30.00
\n\u6700\u5927\u9762\u79ef\u7d22\u5f15: 3
\n\u603b\u9762\u79ef: 84.38<\/p>\n

\u5199\u597d\u4e86\u8d34\u8fc7\u6765，\u6ca1\u95ee\u9898\u5c31\u8fdb\u5165\u7b2c25\u8bfe：\u683c\u5f0f\u5316\u8f93\u51fa\u4e0e\u5e38\u7528\u6807\u51c6\u5e93 👋<\/p>\n

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

use<\/span> std::<\/span><\/span>fmt;<\/span>
\nuse<\/span> std::<\/span><\/span>f64<\/span>::<\/span>consts::<\/span><\/span>PI<\/span>;<\/span><\/p>\n

\/\/ Shape trait，describe \u63d0\u4f9b\u9ed8\u8ba4\u5b9e\u73b0<\/span>
\ntrait<\/span> Shape<\/span> {<\/span>
\n fn<\/span> area<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> f64<\/span>;<\/span>
\n fn<\/span> perimeter<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> f64<\/span>;<\/span><\/p>\n

fn<\/span> describe<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> String<\/span> {<\/span>
\n format!<\/span>(<\/span>"\u9762\u79ef={:.2}, \u5468\u957f={:.2}"<\/span>,<\/span> self<\/span>.<\/span>area<\/span>(<\/span>)<\/span>,<\/span> self<\/span>.<\/span>perimeter<\/span>(<\/span>)<\/span>)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

\/\/ \u4e09\u89d2\u5f62\u7ed3\u6784\u4f53<\/span>
\nstruct<\/span> Triangle<\/span> {<\/span>
\n a:<\/span> f64<\/span>,<\/span>
\n b:<\/span> f64<\/span>,<\/span>
\n c:<\/span> f64<\/span>,<\/span>
\n}<\/span><\/p>\n

impl<\/span> Shape<\/span> for<\/span> Triangle<\/span> {<\/span>
\n fn<\/span> area<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> f64<\/span> {<\/span>
\n let<\/span> s =<\/span> (<\/span>self<\/span>.<\/span>a +<\/span> self<\/span>.<\/span>b +<\/span> self<\/span>.<\/span>c)<\/span> \/<\/span> 2.0<\/span>;<\/span>
\n (<\/span>s *<\/span> (<\/span>s –<\/span> self<\/span>.<\/span>a)<\/span> *<\/span> (<\/span>s –<\/span> self<\/span>.<\/span>b)<\/span> *<\/span> (<\/span>s –<\/span> self<\/span>.<\/span>c)<\/span>)<\/span>.<\/span>sqrt<\/span>(<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> perimeter<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> f64<\/span> {<\/span>
\n self<\/span>.<\/span>a +<\/span> self<\/span>.<\/span>b +<\/span> self<\/span>.<\/span>c
\n }<\/span>
\n}<\/span><\/p>\n

impl<\/span> fmt::<\/span><\/span>Display<\/span> for<\/span> Triangle<\/span> {<\/span>
\n fn<\/span> fmt<\/span>(<\/span>&<\/span>self<\/span>,<\/span> f:<\/span> &<\/span>mut<\/span> fmt::<\/span><\/span>Formatter<\/span><<\/span>'_<\/span>><\/span>)<\/span> -><\/span> fmt::<\/span><\/span>Result<\/span> {<\/span>
\n write!<\/span>(<\/span>f,<\/span> "\u4e09\u89d2\u5f62({},{},{})"<\/span>,<\/span> self<\/span>.<\/span>a,<\/span> self<\/span>.<\/span>b,<\/span> self<\/span>.<\/span>c)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

\/\/ \u6b63\u591a\u8fb9\u5f62<\/span>
\nstruct<\/span> RegularPolygon<\/span> {<\/span>
\n sides:<\/span> usize<\/span>,<\/span>
\n side_length:<\/span> f64<\/span>,<\/span>
\n}<\/span><\/p>\n

impl<\/span> Shape<\/span> for<\/span> RegularPolygon<\/span> {<\/span>
\n fn<\/span> area<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> f64<\/span> {<\/span>
\n let<\/span> n =<\/span> self<\/span>.<\/span>sides as<\/span> f64<\/span>;<\/span>
\n let<\/span> s =<\/span> self<\/span>.<\/span>side_length;<\/span>
\n (<\/span>n *<\/span> s *<\/span> s)<\/span> \/<\/span> (<\/span>4.0<\/span> *<\/span> (<\/span>PI<\/span> \/<\/span> n)<\/span>.<\/span>tan<\/span>(<\/span>)<\/span>)<\/span>
\n }<\/span><\/p>\n

fn<\/span> perimeter<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> f64<\/span> {<\/span>
\n (<\/span>self<\/span>.<\/span>sides as<\/span> f64<\/span>)<\/span> *<\/span> self<\/span>.<\/span>side_length
\n }<\/span>
\n}<\/span><\/p>\n

impl<\/span> fmt::<\/span><\/span>Display<\/span> for<\/span> RegularPolygon<\/span> {<\/span>
\n fn<\/span> fmt<\/span>(<\/span>&<\/span>self<\/span>,<\/span> f:<\/span> &<\/span>mut<\/span> fmt::<\/span><\/span>Formatter<\/span><<\/span>'_<\/span>><\/span>)<\/span> -><\/span> fmt::<\/span><\/span>Result<\/span> {<\/span>
\n write!<\/span>(<\/span>f,<\/span> "\u6b63{}\u8fb9\u5f62(\u8fb9\u957f={})"<\/span>,<\/span> self<\/span>.<\/span>sides,<\/span> self<\/span>.<\/span>side_length)<\/span>
\n }<\/span>
\n}<\/span><\/p>\n

\/\/ \u8fd4\u56de\u9762\u79ef\u6700\u5927\u5f62\u72b6\u7684\u7d22\u5f15<\/span>
\nfn<\/span> largest_shape<\/span>(<\/span>shapes:<\/span> &<\/span>[<\/span>Box<\/span><<\/span>dyn<\/span> Shape<\/span>><\/span>]<\/span>)<\/span> -><\/span> usize<\/span> {<\/span>
\n shapes
\n .<\/span>iter<\/span>(<\/span>)<\/span>
\n .<\/span>enumerate<\/span>(<\/span>)<\/span>
\n .<\/span>max_by<\/span>(<\/span>|<\/span>(<\/span>_,<\/span> s1)<\/span>,<\/span> (<\/span>_,<\/span> s2)<\/span>|<\/span><\/span> s1.<\/span>area<\/span>(<\/span>)<\/span>.<\/span>partial_cmp<\/span>(<\/span>&<\/span>s2.<\/span>area<\/span>(<\/span>)<\/span>)<\/span>.<\/span>unwrap<\/span>(<\/span>)<\/span>)<\/span>
\n .<\/span>map<\/span>(<\/span>|<\/span>(<\/span>idx,<\/span> _)<\/span>|<\/span><\/span> idx)<\/span>
\n .<\/span>unwrap<\/span>(<\/span>)<\/span>
\n}<\/span><\/p>\n

\/\/ \u5168\u90e8\u5f62\u72b6\u9762\u79ef\u4e4b\u548c<\/span>
\nfn<\/span> total_area<\/span>(<\/span>shapes:<\/span> &<\/span>[<\/span>Box<\/span><<\/span>dyn<\/span> Shape<\/span>><\/span>]<\/span>)<\/span> -><\/span> f64<\/span> {<\/span>
\n shapes.<\/span>iter<\/span>(<\/span>)<\/span>.<\/span>map<\/span>(<\/span>|<\/span>s|<\/span><\/span> s.<\/span>area<\/span>(<\/span>)<\/span>)<\/span>.<\/span>sum<\/span>(<\/span>)<\/span>
\n}<\/span><\/p>\n

fn<\/span> main<\/span>(<\/span>)<\/span> {<\/span>
\n \/\/ \u521b\u5efa\u52a8\u6001\u5f62\u72b6\u6570\u7ec4<\/span>
\n let<\/span> shapes:<\/span> Vec<\/span><<\/span>Box<\/span><<\/span>dyn<\/span> Shape<\/span>>><\/span> =<\/span> vec!<\/span>[<\/span>
\n Box<\/span>::<\/span>new<\/span>(<\/span>Triangle<\/span> {<\/span> a:<\/span> 3.0<\/span>,<\/span> b:<\/span> 4.0<\/span>,<\/span> c:<\/span> 5.0<\/span> }<\/span>)<\/span>,<\/span>
\n Box<\/span>::<\/span>new<\/span>(<\/span>RegularPolygon<\/span> {<\/span> sides:<\/span> 4<\/span>,<\/span> side_length:<\/span> 5.0<\/span> }<\/span>)<\/span>,<\/span>
\n Box<\/span>::<\/span>new<\/span>(<\/span>RegularPolygon<\/span> {<\/span> sides:<\/span> 6<\/span>,<\/span> side_length:<\/span> 3.0<\/span> }<\/span>)<\/span>,<\/span>
\n Box<\/span>::<\/span>new<\/span>(<\/span>Triangle<\/span> {<\/span> a:<\/span> 5.0<\/span>,<\/span> b:<\/span> 12.0<\/span>,<\/span> c:<\/span> 13.0<\/span> }<\/span>)<\/span>,<\/span>
\n ]<\/span>;<\/span><\/p>\n

\/\/ \u904d\u5386\u6253\u5370<\/span>
\n for<\/span> s in<\/span> &<\/span>shapes {<\/span>
\n \/\/ \u9700\u8981\u540c\u65f6\u62ff\u5230Display\u548cShape，\u8fd9\u91cc\u5206\u5f00\u5904\u7406；\u4e3a\u4e86\u65b9\u4fbf\u6211\u4eec\u91cd\u65b0\u5305\u88c5<\/span>
\n \/\/ \u4e3a\u4e86\u6ee1\u8db3\u6253\u5370 "\u4e09\u89d2\u5f62(3,4,5): \u9762\u79ef=6.00, \u5468\u957f=12.00"，<\/span>
\n \/\/ dyn Shape \u672c\u8eab\u6ca1\u6709Display，\u6240\u4ee5\u6211\u4eec\u6539\u7528\u6a21\u5f0f\u5339\u914d\u6253\u5370（\u7ec3\u4e60\u7248\u672c）<\/span>
\n \/\/ \u4e0b\u9762\u4e3b\u5faa\u73af\u5b8c\u6574\u5b9e\u73b0<\/span>
\n }<\/span><\/p>\n

\/\/ \u65b9\u6848：\u91cd\u5efa\u5e26\u6253\u5370\u7684\u7248\u672c，\u5b8c\u6574main\u5b9e\u73b0：<\/span>
\n let<\/span> tri1 =<\/span> Triangle<\/span> {<\/span> a:<\/span> 3.0<\/span>,<\/span> b:<\/span> 4.0<\/span>,<\/span> c:<\/span> 5.0<\/span> }<\/span>;<\/span>
\n let<\/span> sq =<\/span> RegularPolygon<\/span> {<\/span> sides:<\/span> 4<\/span>,<\/span> side_length:<\/span> 5.0<\/span> }<\/span>;<\/span>
\n let<\/span> hex =<\/span> RegularPolygon<\/span> {<\/span> sides:<\/span> 6<\/span>,<\/span> side_length:<\/span> 3.0<\/span> }<\/span>;<\/span>
\n let<\/span> tri2 =<\/span> Triangle<\/span> {<\/span> a:<\/span> 5.0<\/span>,<\/span> b:<\/span> 12.0<\/span>,<\/span> c:<\/span> 13.0<\/span> }<\/span>;<\/span><\/p>\n

let<\/span> shape_vec:<\/span> Vec<\/span><<\/span>Box<\/span><<\/span>dyn<\/span> Shape<\/span>>><\/span> =<\/span> vec!<\/span>[<\/span>
\n Box<\/span>::<\/span>new<\/span>(<\/span>tri1)<\/span>,<\/span>
\n Box<\/span>::<\/span>new<\/span>(<\/span>sq)<\/span>,<\/span>
\n Box<\/span>::<\/span>new<\/span>(<\/span>hex)<\/span>,<\/span>
\n Box<\/span>::<\/span>new<\/span>(<\/span>tri2)<\/span>,<\/span>
\n ]<\/span>;<\/span><\/p>\n

\/\/ \u6ce8\u610f：dyn Shape \u4e0d\u80fd\u76f4\u63a5Display；\u4e3a\u4e86\u5b8c\u6210\u9898\u76ee\u8f93\u51fa，\u4e0b\u9762\u628a\u5bf9\u8c61\u518d\u5b58\u4e00\u4efd\u7528\u4e8e\u6253\u5370<\/span>
\n \/\/ \u5b8c\u6574\u7248main（\u4fdd\u5b58\u5404\u4e2a\u5b9e\u4f53\u7528\u4e8e\u683c\u5f0f\u5316\u8f93\u51fa）<\/span>
\n let<\/span> items =<\/span> [<\/span>
\n (<\/span>&<\/span>Triangle<\/span> {<\/span> a:<\/span> 3.0<\/span>,<\/span> b:<\/span> 4.0<\/span>,<\/span> c:<\/span> 5.0<\/span> }<\/span>)<\/span> as<\/span> &<\/span>dyn<\/span> fmt::<\/span><\/span>Display<\/span>,<\/span>
\n &<\/span>RegularPolygon<\/span> {<\/span> sides:<\/span> 4<\/span>,<\/span> side_length:<\/span> 5.0<\/span> }<\/span> as<\/span> &<\/span>dyn<\/span> fmt::<\/span><\/span>Display<\/span>,<\/span>
\n &<\/span>RegularPolygon<\/span> {<\/span> sides:<\/span> 6<\/span>,<\/span> side_length:<\/span> 3.0<\/span> }<\/span> as<\/span> &<\/span>dyn<\/span> fmt::<\/span><\/span>Display<\/span>,<\/span>
\n &<\/span>Triangle<\/span> {<\/span> a:<\/span> 5.0<\/span>,<\/span> b:<\/span> 12.0<\/span>,<\/span> c:<\/span> 13.0<\/span> }<\/span> as<\/span> &<\/span>dyn<\/span> fmt::<\/span><\/span>Display<\/span>,<\/span>
\n ]<\/span>;<\/span><\/p>\n

for<\/span> i in<\/span> 0<\/span>..<\/span>shape_vec.<\/span>len<\/span>(<\/span>)<\/span> {<\/span>
\n println!<\/span>(<\/span>"{}: {}"<\/span>,<\/span> items[<\/span>i]<\/span>,<\/span> shape_vec[<\/span>i]<\/span>.<\/span>describe<\/span>(<\/span>)<\/span>)<\/span>;<\/span>
\n }<\/span><\/p>\n

let<\/span> max_idx =<\/span> largest_shape<\/span>(<\/span>&<\/span>shape_vec)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u6700\u5927\u9762\u79ef\u7d22\u5f15: {}"<\/span>,<\/span> max_idx)<\/span>;<\/span><\/p>\n

let<\/span> sum =<\/span> total_area<\/span>(<\/span>&<\/span>shape_vec)<\/span>;<\/span>
\n println!<\/span>(<\/span>"\u603b\u9762\u79ef: {:.2}"<\/span>,<\/span> sum)<\/span>;<\/span>
\n}<\/span><\/p>\n

\u8fd0\u884c\u8f93\u51fa<\/p>\n

plaintext<\/p>\n

\u4e09\u89d2\u5f62(3,4,5): \u9762\u79ef=6.00, \u5468\u957f=12.00
\n\u6b634\u8fb9\u5f62(\u8fb9\u957f=5): \u9762\u79ef=25.00, \u5468\u957f=20.00
\n\u6b636\u8fb9\u5f62(\u8fb9\u957f=3): \u9762\u79ef=23.38, \u5468\u957f=18.00
\n\u4e09\u89d2\u5f62(5,12,13): \u9762\u79ef=30.00, \u5468\u957f=30.00
\n\u6700\u5927\u9762\u79ef\u7d22\u5f15: 3
\n\u603b\u9762\u79ef: 84.38<\/p>\n

\u6838\u5fc3\u77e5\u8bc6\u70b9<\/h2>\n

1. Trait \u9ed8\u8ba4\u65b9\u6cd5<\/p>\n

fn<\/span> describe<\/span>(<\/span>&<\/span>self<\/span>)<\/span> -><\/span> String<\/span> {<\/span> …<\/span> }<\/span><\/p>\n

\u6ca1\u6709 &self \u524d\u9762\u6ca1\u6709 dyn ，\u76f4\u63a5\u5199\u5728trait\u91cc\u9762，\u4e0d\u7528\u6bcf\u4e2a\u5b9e\u73b0\u8005\u91cd\u590d\u5b9e\u73b0\u3002<\/p>\n

2. \u6d77\u4f26\u516c\u5f0f（\u4e09\u89d2\u5f62\u9762\u79ef）<\/p>\n

s=<\/span>(<\/span>a+<\/span>b+<\/span>c)<\/span>\/<\/span>2<\/span>,<\/span>\\\\quad area=<\/span>\\\\sqrt{<\/span>s<\/span>(<\/span>s–<\/span>a)<\/span>(<\/span>s–<\/span>b)<\/span>(<\/span>s–<\/span>c)<\/span>}<\/span><\/p>\n

3. \u6b63\u591a\u8fb9\u5f62\u9762\u79ef\u516c\u5f0f<\/p>\n

A<\/span>=<\/span>\\\\dfrac{<\/span>n\\\\cdot s^<\/span>{<\/span>2<\/span>}<\/span>}<\/span>{<\/span>4<\/span>\\\\cdot\\\\tan<\/span>(<\/span>\\\\pi\/<\/span>n)<\/span>}<\/span><\/p>\n

\u9700\u8981 std::f64::consts::PI \u3002<\/p>\n

**4. Trait \u5bf9\u8c61（\u52a8\u6001\u5206\u53d1） Box **<\/p>\n