{"id":71965,"date":"2026-02-04T17:41:19","date_gmt":"2026-02-04T09:41:19","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/71965.html"},"modified":"2026-02-04T17:41:19","modified_gmt":"2026-02-04T09:41:19","slug":"c-stdoptional%e8%af%a6%e8%a7%a3-%e8%96%9b%e5%ae%9a%e8%b0%94%e7%9a%84%e7%9b%92%e5%ad%90%ef%bc%81","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/71965.html","title":{"rendered":"C++ std::optional\u8be6\u89e3-\u859b\u5b9a\u8c14\u7684\u201c\u76d2\u5b50\u201d\uff01"},"content":{"rendered":"<\/p>\n<h4>C&#043;&#043; std::optional\u8be6\u89e3-\u859b\u5b9a\u8c14\u7684\u201c\u76d2\u5b50\u201d&#xff01;<\/h4>\n<ul>\n<li>\u4e00\u3001std::optional\u8be6\u89e3<\/li>\n<li>\n<ul>\n<li>1\u3001\u4ec0\u4e48\u662f &#096;std::optional&#096;&#xff1f;<\/li>\n<li>2\u3001\u4e3a\u4ec0\u4e48\u9700\u8981 &#096;std::optional&#096;&#xff1f;<\/li>\n<li>3\u3001\u6838\u5fc3\u64cd\u4f5c\u4e0e\u6210\u5458\u51fd\u6570<\/li>\n<li>\n<ul>\n<li>3.1 \u3001\u6784\u9020\u4e0e\u8d4b\u503c<\/li>\n<li>3.2\u3001 \u72b6\u6001\u68c0\u67e5<\/li>\n<li>3.3\u3001 \u503c\u8bbf\u95ee<\/li>\n<li>3.4 \u3001\u4fee\u6539\u4e0e\u9500\u6bc1<\/li>\n<li>3.5\u3001\u8bbf\u95ee\u5305\u542b\u7684\u503c (C&#043;&#043;23 \u65b0\u589e)<\/li>\n<\/ul>\n<\/li>\n<li>4\u3001 \u5178\u578b\u4f7f\u7528\u573a\u666f<\/li>\n<li>5\u3001\u6ce8\u610f\u4e8b\u9879<\/li>\n<li>6\u3001 \u793a\u4f8b\u4ee3\u7801<\/li>\n<\/ul>\n<\/li>\n<li>\u4e8c\u3001\u4ee3\u7801\u793a\u4f8b<\/li>\n<\/ul>\n<p><img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2026\/02\/20260204094115-6983143b364ad.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/><\/p>\n<h2>\u4e00\u3001std::optional\u8be6\u89e3<\/h2>\n<h3>1\u3001\u4ec0\u4e48\u662f std::optional&#xff1f;<\/h3>\n<p>std::optional \u662f C&#043;&#043;17 \u5f15\u5165\u7684\u4e00\u4e2a\u6a21\u677f\u7c7b&#xff0c;\u5b83\u7528\u4e8e\u8868\u793a\u4e00\u4e2a \u53ef\u80fd\u5305\u542b\u503c&#xff0c;\u4e5f\u53ef\u80fd\u4e0d\u5305\u542b\u503c&#xff08;\u5373\u4e3a\u201c\u7a7a\u201d&#xff09; \u7684\u5c01\u88c5\u3002\u5b83\u63d0\u4f9b\u4e86\u4e00\u79cd\u7c7b\u578b\u5b89\u5168\u3001\u8868\u8fbe\u6e05\u6670\u7684\u65b9\u5f0f\u6765\u5904\u7406\u90a3\u4e9b\u4e0d\u603b\u662f\u6709\u6709\u6548\u7ed3\u679c\u7684\u64cd\u4f5c&#xff08;\u6bd4\u5982\u67e5\u627e\u3001\u89e3\u6790\u3001\u8ba1\u7b97\u7b49&#xff09;\u3002<\/p>\n<ul>\n<li>\u6838\u5fc3\u601d\u60f3&#xff1a;\u4e00\u4e2a std::optional&lt;T&gt; \u5bf9\u8c61\u8981\u4e48\u6301\u6709\u4e00\u4e2a\u7c7b\u578b\u4e3a T \u7684\u503c&#xff0c;\u8981\u4e48\u4ec0\u4e48\u90fd\u4e0d\u6301\u6709&#xff08;\u8868\u793a\u4e3a std::nullopt&#xff09;\u3002<\/li>\n<li>\u66ff\u4ee3\u65b9\u6848&#xff1a;\u5728\u5f15\u5165 std::optional \u4e4b\u524d&#xff0c;\u901a\u5e38\u4f7f\u7528\u7279\u6b8a\u503c&#xff08;\u5982 -1, nullptr, std::string::npos&#xff09;\u3001bool \u6807\u5fd7\u4f4d\u52a0\u4e00\u4e2a\u503c\u53d8\u91cf\u3001\u6216\u8fd4\u56de\u6307\u9488&#xff08;\u53ef\u80fd\u4e3a nullptr&#xff09;\u7b49\u65b9\u5f0f\u6765\u8868\u793a\u53ef\u9009\u503c\u3002std::optional \u63d0\u4f9b\u4e86\u4e00\u79cd\u66f4\u6807\u51c6\u3001\u66f4\u5b89\u5168\u3001\u66f4\u6613\u4e8e\u7406\u89e3\u7684\u65b9\u5f0f\u3002<\/li>\n<\/ul>\n<h3>2\u3001\u4e3a\u4ec0\u4e48\u9700\u8981 std::optional&#xff1f;<\/h3>\n<ul>\n<li>\u7c7b\u578b\u5b89\u5168&#xff1a;\u660e\u786e\u533a\u5206\u6709\u503c\u548c\u65e0\u503c\u7684\u72b6\u6001&#xff0c;\u7f16\u8bd1\u5668\u53ef\u4ee5\u68c0\u67e5&#xff0c;\u907f\u514d\u8bef\u7528\u65e0\u6548\u503c\u3002<\/li>\n<li>\u8868\u8fbe\u6e05\u6670&#xff1a;\u4ee3\u7801\u610f\u56fe\u66f4\u660e\u786e&#xff0c;\u770b\u5230 std::optional \u5c31\u77e5\u9053\u8fd9\u4e2a\u503c\u53ef\u80fd\u4e0d\u5b58\u5728\u3002<\/li>\n<li>\u907f\u514d\u9b54\u672f\u503c&#xff1a;\u4e0d\u518d\u9700\u8981\u4f7f\u7528\u7279\u5b9a\u7684\u3001\u6709\u65f6\u96be\u4ee5\u8bb0\u5fc6\u6216\u5bb9\u6613\u6df7\u6dc6\u7684\u201c\u65e0\u6548\u503c\u201d\u6765\u8868\u793a\u7f3a\u5931\u3002<\/li>\n<li>\u66f4\u597d\u7684\u63a5\u53e3\u8bbe\u8ba1&#xff1a;\u51fd\u6570\u53ef\u4ee5\u6e05\u6670\u5730\u8fd4\u56de\u4e00\u4e2a\u53ef\u80fd\u4e0d\u5b58\u5728\u7684\u7ed3\u679c&#xff0c;\u800c\u4e0d\u662f\u901a\u8fc7\u8f93\u51fa\u53c2\u6570\u6216\u5f02\u5e38&#xff08;\u5728\u67d0\u4e9b\u573a\u666f\u4e0b\u5f02\u5e38\u53ef\u80fd\u592a\u91cd&#xff09;\u6765\u4f20\u9012\u72b6\u6001\u3002<\/li>\n<li>\u6548\u7387&#xff1a;\u901a\u5e38&#xff0c;std::optional&lt;T&gt; \u7684\u5185\u5b58\u5360\u7528\u662f sizeof(T) &#043; sizeof(bool) \u52a0\u4e0a\u53ef\u80fd\u7684\u5bf9\u9f50\u586b\u5145\u3002\u5b83\u901a\u5e38\u6bd4\u4f7f\u7528\u52a8\u6001\u5185\u5b58\u5206\u914d&#xff08;\u5982 std::unique_ptr&#xff09;\u66f4\u8f7b\u91cf\u3002<\/li>\n<\/ul>\n<h3>3\u3001\u6838\u5fc3\u64cd\u4f5c\u4e0e\u6210\u5458\u51fd\u6570<\/h3>\n<h4>3.1 \u3001\u6784\u9020\u4e0e\u8d4b\u503c<\/h4>\n<ul>\n<li>\u9ed8\u8ba4\u6784\u9020&#xff1a;\u521b\u5efa\u4e00\u4e2a\u4e0d\u5305\u542b\u503c\u7684 optional \u5bf9\u8c61&#xff08;\u7a7a\u72b6\u6001&#xff09;\u3002std<span class=\"token double-colon punctuation\">::<\/span>optional<span class=\"token operator\">&lt;<\/span><span class=\"token keyword\">int<\/span><span class=\"token operator\">&gt;<\/span> optInt<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u7a7a\u7684 optional<\/span>\n <\/li>\n<li>std::nullopt \u6784\u9020&#xff1a;\u663e\u5f0f\u6784\u9020\u4e00\u4e2a\u7a7a optional\u3002std<span class=\"token double-colon punctuation\">::<\/span>optional<span class=\"token operator\">&lt;<\/span>std<span class=\"token double-colon punctuation\">::<\/span>string<span class=\"token operator\">&gt;<\/span> optStr <span class=\"token operator\">&#061;<\/span> std<span class=\"token double-colon punctuation\">::<\/span>nullopt<span class=\"token punctuation\">;<\/span>\n <\/li>\n<li>\u503c\u521d\u59cb\u5316&#xff1a;\u7528\u7ed9\u5b9a\u7684\u503c\u6784\u9020\u4e00\u4e2a\u5305\u542b\u8be5\u503c\u7684 optional\u3002std<span class=\"token double-colon punctuation\">::<\/span>optional<span class=\"token operator\">&lt;<\/span><span class=\"token keyword\">double<\/span><span class=\"token operator\">&gt;<\/span> <span class=\"token function\">optDbl<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">3.14159<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u5305\u542b pi<\/span>\n <\/li>\n<li>std::in_place \u6784\u9020&#xff1a;\u7528\u4e8e\u76f4\u63a5\u539f\u5730\u6784\u9020\u5305\u542b\u7684\u5bf9\u8c61&#xff0c;\u7279\u522b\u662f\u5f53 T \u7684\u6784\u9020\u51fd\u6570\u9700\u8981\u591a\u4e2a\u53c2\u6570&#xff0c;\u6216\u8005\u4f60\u60f3\u907f\u514d\u4e34\u65f6\u5bf9\u8c61\u65f6\u3002std<span class=\"token double-colon punctuation\">::<\/span>optional<span class=\"token operator\">&lt;<\/span>std<span class=\"token double-colon punctuation\">::<\/span>complex<span class=\"token operator\">&lt;<\/span><span class=\"token keyword\">double<\/span><span class=\"token operator\">&gt;&gt;<\/span> <span class=\"token function\">optComplex<\/span><span class=\"token punctuation\">(<\/span>std<span class=\"token double-colon punctuation\">::<\/span>in_place<span class=\"token punctuation\">,<\/span> <span class=\"token number\">1.0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">2.0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u6784\u9020 complex(1.0, 2.0)<\/span>\n <\/li>\n<li>\u62f7\u8d1d\/\u79fb\u52a8\u6784\u9020\u4e0e\u8d4b\u503c&#xff1a;\u652f\u6301\u4ece\u53e6\u4e00\u4e2a optional \u62f7\u8d1d\u6216\u79fb\u52a8\u3002<\/li>\n<li>\u8d4b\u503c&#xff1a;\u53ef\u4ee5\u4f7f\u7528 &#061; \u6765\u8d4b\u503c\u4e00\u4e2a\u503c\u3001std::nullopt \u6216\u53e6\u4e00\u4e2a optional\u3002optInt <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">42<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u73b0\u5728\u5305\u542b 42<\/span><br \/>\noptInt <span class=\"token operator\">&#061;<\/span> std<span class=\"token double-colon punctuation\">::<\/span>nullopt<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u53d8\u4e3a\u7a7a<\/span>\n <\/li>\n<\/ul>\n<h4>3.2\u3001 \u72b6\u6001\u68c0\u67e5<\/h4>\n<ul>\n<li>has_value() \/ operator bool&#xff1a;\u68c0\u67e5 optional \u662f\u5426\u5305\u542b\u503c\u3002\u4e24\u8005\u901a\u5e38\u7b49\u4ef7\u3002<span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>optInt<span class=\"token punctuation\">.<\/span><span class=\"token function\">has_value<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span> <span class=\"token comment\">\/* \u6709\u503c *\/<\/span> <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>optInt<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span> <span class=\"token comment\">\/* \u6709\u503c&#xff0c;\u5e38\u7528\u8fd9\u79cd\u7b80\u6d01\u5199\u6cd5 *\/<\/span> <span class=\"token punctuation\">}<\/span>\n <\/li>\n<li>operator &#061;&#061; std::nullopt&#xff1a;\u68c0\u67e5\u662f\u5426\u4e3a\u7a7a\u3002<span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>optStr <span class=\"token operator\">&#061;&#061;<\/span> std<span class=\"token double-colon punctuation\">::<\/span>nullopt<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span> <span class=\"token comment\">\/* \u7a7a *\/<\/span> <span class=\"token punctuation\">}<\/span>\n <\/li>\n<\/ul>\n<h4>3.3\u3001 \u503c\u8bbf\u95ee<\/h4>\n<p>\u8b66\u544a&#xff1a;\u5728 optional \u4e3a\u7a7a\u65f6\u8bbf\u95ee\u5176\u503c\u662f\u672a\u5b9a\u4e49\u884c\u4e3a&#xff08;\u901a\u5e38\u4f1a\u5bfc\u81f4\u7a0b\u5e8f\u5d29\u6e83\u6216\u4e0d\u53ef\u9884\u77e5\u7684\u7ed3\u679c&#xff09;\u3002\u8bbf\u95ee\u524d\u5fc5\u987b\u68c0\u67e5\u662f\u5426\u6709\u503c\u3002<\/p>\n<ul>\n<li>value()&#xff1a;\u8fd4\u56de\u5305\u542b\u503c\u7684\u5f15\u7528\u3002\u5982\u679c\u4e3a\u7a7a&#xff0c;\u5219\u629b\u51fa std::bad_optional_access \u5f02\u5e38\u3002<span class=\"token keyword\">try<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token keyword\">int<\/span> x <span class=\"token operator\">&#061;<\/span> optInt<span class=\"token punctuation\">.<\/span><span class=\"token function\">value<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u5b89\u5168\u8bbf\u95ee&#xff0c;\u53ef\u80fd\u629b\u5f02\u5e38<\/span><br \/>\n<span class=\"token punctuation\">}<\/span> <span class=\"token keyword\">catch<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">const<\/span> std<span class=\"token double-colon punctuation\">::<\/span>bad_optional_access<span class=\"token operator\">&amp;<\/span> e<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u5904\u7406\u7a7a\u7684\u60c5\u51b5<\/span><br \/>\n<span class=\"token punctuation\">}<\/span>\n <\/li>\n<li>operator*&#xff1a;\u8fd4\u56de\u5305\u542b\u503c\u7684\u5f15\u7528\u3002\u4e0d\u68c0\u67e5\u662f\u5426\u4e3a\u7a7a&#xff01;\u4ec5\u5728\u786e\u5b9a\u6709\u503c\u65f6\u4f7f\u7528\u3002<span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>optDbl<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token keyword\">double<\/span> y <span class=\"token operator\">&#061;<\/span> <span class=\"token operator\">*<\/span>optDbl<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u89e3\u5f15\u7528\u8bbf\u95ee<\/span><br \/>\n<span class=\"token punctuation\">}<\/span>\n <\/li>\n<li>operator-&gt;&#xff1a;\u8fd4\u56de\u6307\u5411\u5305\u542b\u503c\u7684\u6307\u9488\u3002\u4e0d\u68c0\u67e5\u662f\u5426\u4e3a\u7a7a&#xff01;\u4ec5\u5728\u786e\u5b9a\u6709\u503c\u65f6\u4f7f\u7528\u3002std<span class=\"token double-colon punctuation\">::<\/span>optional<span class=\"token operator\">&lt;<\/span>std<span class=\"token double-colon punctuation\">::<\/span>vector<span class=\"token operator\">&lt;<\/span><span class=\"token keyword\">int<\/span><span class=\"token operator\">&gt;&gt;<\/span> optVec<span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token comment\">\/\/ &#8230; \u53ef\u80fd\u7ed9 optVec \u8d4b\u503c\u4e00\u4e2a vector &#8230;<\/span><br \/>\n<span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>optVec<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    size_t sz <span class=\"token operator\">&#061;<\/span> optVec<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">size<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u4f7f\u7528 -&gt; \u8bbf\u95ee\u6210\u5458<\/span><br \/>\n<span class=\"token punctuation\">}<\/span>\n <\/li>\n<li>value_or(U&amp;&amp; default_value)&#xff1a;\u5982\u679c\u5305\u542b\u503c&#xff0c;\u5219\u8fd4\u56de\u8be5\u503c&#xff1b;\u5426\u5219\u8fd4\u56de\u63d0\u4f9b\u7684 default_value\u3002\u8fd9\u662f\u5b89\u5168\u83b7\u53d6\u503c\u7684\u4fbf\u6377\u65b9\u5f0f\u3002<span class=\"token keyword\">int<\/span> safeValue <span class=\"token operator\">&#061;<\/span> optInt<span class=\"token punctuation\">.<\/span><span class=\"token function\">value_or<\/span><span class=\"token punctuation\">(<\/span><span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u5982\u679c optInt \u4e3a\u7a7a&#xff0c;\u5219\u8fd4\u56de -1<\/span>\n <\/li>\n<\/ul>\n<h4>3.4 \u3001\u4fee\u6539\u4e0e\u9500\u6bc1<\/h4>\n<ul>\n<li>emplace(args&#8230;)&#xff1a;\u5728\u539f\u5730\u6784\u9020\u4e00\u4e2a\u65b0\u503c&#xff08;\u66ff\u6362\u5f53\u524d\u53ef\u80fd\u5b58\u5728\u7684\u503c&#xff09;\u3002\u53c2\u6570 args&#8230; \u4f20\u9012\u7ed9 T \u7684\u6784\u9020\u51fd\u6570\u3002optStr<span class=\"token punctuation\">.<\/span><span class=\"token function\">emplace<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;Hello, Optional!&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u6784\u9020\u4e00\u4e2a string<\/span>\n <\/li>\n<li>reset()&#xff1a;\u9500\u6bc1\u5305\u542b\u7684\u503c&#xff08;\u5982\u679c\u5b58\u5728&#xff09;&#xff0c;\u5e76\u5c06 optional \u7f6e\u4e3a\u7a7a\u72b6\u6001\u3002\u7b49\u4ef7\u4e8e opt &#061; std::nullopt;\u3002optComplex<span class=\"token punctuation\">.<\/span><span class=\"token function\">reset<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u73b0\u5728\u4e3a\u7a7a<\/span>\n <\/li>\n<li>swap&#xff1a;\u4ea4\u6362\u4e24\u4e2a optional \u5bf9\u8c61\u7684\u5185\u5bb9\u3002<\/li>\n<\/ul>\n<h4>3.5\u3001\u8bbf\u95ee\u5305\u542b\u7684\u503c (C&#043;&#043;23 \u65b0\u589e)<\/h4>\n<ul>\n<li>and_then&#xff1a;\u5982\u679c\u5305\u542b\u503c&#xff0c;\u5219\u5e94\u7528\u7ed9\u5b9a\u7684\u51fd\u6570\u5230\u8be5\u503c\u4e0a&#xff08;\u8be5\u51fd\u6570\u5e94\u8fd4\u56de\u53e6\u4e00\u4e2a optional&#xff09;&#xff0c;\u5426\u5219\u8fd4\u56de\u7a7a optional\u3002\u7528\u4e8e\u94fe\u5f0f\u8c03\u7528\u3002<\/li>\n<li>transform&#xff1a;\u5982\u679c\u5305\u542b\u503c&#xff0c;\u5219\u5e94\u7528\u7ed9\u5b9a\u7684\u51fd\u6570\u5230\u8be5\u503c\u4e0a&#xff08;\u8be5\u51fd\u6570\u8fd4\u56de\u4e00\u4e2a\u65b0\u7c7b\u578b\u7684\u503c&#xff09;&#xff0c;\u5e76\u5c06\u7ed3\u679c\u5305\u88c5\u5728 optional \u4e2d\u8fd4\u56de&#xff1b;\u5426\u5219\u8fd4\u56de\u7a7a optional\u3002<\/li>\n<li>or_else&#xff1a;\u5982\u679c\u4e3a\u7a7a&#xff0c;\u5219\u8c03\u7528\u7ed9\u5b9a\u7684\u51fd\u6570&#xff08;\u8be5\u51fd\u6570\u5e94\u8fd4\u56de\u4e00\u4e2a optional&#xff09;&#xff0c;\u5426\u5219\u8fd4\u56de\u5f53\u524d optional\u3002<\/li>\n<\/ul>\n<h3>4\u3001 \u5178\u578b\u4f7f\u7528\u573a\u666f<\/h3>\n<li>\u51fd\u6570\u8fd4\u56de\u53ef\u80fd\u65e0\u6548\u7684\u7ed3\u679c&#xff1a;std<span class=\"token double-colon punctuation\">::<\/span>optional<span class=\"token operator\">&lt;<\/span><span class=\"token keyword\">int<\/span><span class=\"token operator\">&gt;<\/span> <span class=\"token function\">find_id_by_name<\/span><span class=\"token punctuation\">(<\/span><span class=\"token keyword\">const<\/span> std<span class=\"token double-colon punctuation\">::<\/span>string<span class=\"token operator\">&amp;<\/span> name<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ &#8230; \u67e5\u627e\u903b\u8f91 &#8230;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>found<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> found_id<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token keyword\">return<\/span> std<span class=\"token double-colon punctuation\">::<\/span>nullopt<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u672a\u627e\u5230<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token keyword\">auto<\/span> idOpt <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">find_id_by_name<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;Alice&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>idOpt<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token function\">use_id<\/span><span class=\"token punctuation\">(<\/span><span class=\"token operator\">*<\/span>idOpt<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span>\n <\/li>\n<li>\u89e3\u6790\/\u8f6c\u6362\u53ef\u80fd\u5931\u8d25&#xff1a;std<span class=\"token double-colon punctuation\">::<\/span>optional<span class=\"token operator\">&lt;<\/span><span class=\"token keyword\">int<\/span><span class=\"token operator\">&gt;<\/span> <span class=\"token function\">safe_stoi<\/span><span class=\"token punctuation\">(<\/span><span class=\"token keyword\">const<\/span> std<span class=\"token double-colon punctuation\">::<\/span>string<span class=\"token operator\">&amp;<\/span> str<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token keyword\">try<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> std<span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">stoi<\/span><span class=\"token punctuation\">(<\/span>str<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span> <span class=\"token keyword\">catch<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">.<\/span><span class=\"token punctuation\">.<\/span><span class=\"token punctuation\">.<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> std<span class=\"token double-colon punctuation\">::<\/span>nullopt<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token punctuation\">}<\/span>\n <\/li>\n<li>\u5ef6\u8fdf\u521d\u59cb\u5316&#xff1a;\u6210\u5458\u53d8\u91cf\u53ef\u80fd\u4e0d\u4f1a\u5728\u6784\u9020\u51fd\u6570\u4e2d\u521d\u59cb\u5316&#xff0c;\u800c\u662f\u5728\u540e\u7eed\u67d0\u4e2a\u65b9\u6cd5\u4e2d\u521d\u59cb\u5316\u3002<\/li>\n<li>\u66ff\u4ee3\u6307\u9488\u8868\u793a\u53ef\u9009\u5bf9\u8c61&#xff1a;\u5f53\u5bf9\u8c61\u672c\u8eab\u662f\u53ef\u62f7\u8d1d\/\u53ef\u79fb\u52a8\u7684&#xff0c;\u4e14\u4f60\u4e0d\u60f3\u4f7f\u7528\u52a8\u6001\u5185\u5b58\u5206\u914d\u65f6\u3002<\/li>\n<h3>5\u3001\u6ce8\u610f\u4e8b\u9879<\/h3>\n<ul>\n<li>\u8bbf\u95ee\u524d\u68c0\u67e5&#xff1a;\u8fd9\u662f\u6700\u91cd\u8981\u7684\u89c4\u5219&#xff01;\u6c38\u8fdc\u4e0d\u8981\u5bf9\u53ef\u80fd\u4e3a\u7a7a\u7684 optional \u4f7f\u7528 operator* \u6216 operator-&gt;\u3002\u4f18\u5148\u8003\u8651 value_or \u6216\u5148\u68c0\u67e5 has_value()\/operator bool\u3002<\/li>\n<li>\u6027\u80fd&#xff1a;std::optional \u901a\u5e38\u6ca1\u6709\u52a8\u6001\u5185\u5b58\u5206\u914d\u7684\u5f00\u9500\u3002\u5176\u5927\u5c0f\u901a\u5e38\u662f sizeof(T) &#043; sizeof(bool) \u52a0\u4e0a\u53ef\u80fd\u7684\u5bf9\u9f50\u586b\u5145\u3002\u5bf9\u4e8e\u5c0f\u5bf9\u8c61&#xff0c;\u6548\u7387\u5f88\u9ad8\u3002<\/li>\n<li>\u4e0e std::variant \u7684\u533a\u522b&#xff1a;std::optional&lt;T&gt; \u53ef\u4ee5\u770b\u4f5c\u662f std::variant&lt;std::monostate, T&gt; \u7684\u4e00\u4e2a\u7279\u4f8b\u548c\u7b80\u5316\u3002std::variant \u7528\u4e8e\u8868\u793a\u591a\u4e2a\u53ef\u80fd\u7c7b\u578b\u4e2d\u7684\u4e00\u4e2a\u3002<\/li>\n<li>\u4e0e std::expected (C&#043;&#043;23\u63d0\u6848) \u7684\u533a\u522b&#xff1a;std::expected&lt;T, E&gt; \u7528\u4e8e\u8868\u793a\u4e00\u4e2a\u53ef\u80fd\u5305\u542b\u503c T \u6216\u9519\u8bef E \u7684\u7ed3\u679c&#xff0c;\u6bd4 optional \u80fd\u643a\u5e26\u66f4\u591a\u9519\u8bef\u4fe1\u606f\u3002<\/li>\n<\/ul>\n<h3>6\u3001 \u793a\u4f8b\u4ee3\u7801<\/h3>\n<p><span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;optional&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;iostream&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;string&gt;<\/span><\/span><\/p>\n<p>std<span class=\"token double-colon punctuation\">::<\/span>optional<span class=\"token operator\">&lt;<\/span>std<span class=\"token double-colon punctuation\">::<\/span>string<span class=\"token operator\">&gt;<\/span> <span class=\"token function\">create_greeting<\/span><span class=\"token punctuation\">(<\/span><span class=\"token keyword\">bool<\/span> formal<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>formal<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token string\">&#034;Good day&#034;<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u5305\u542b\u503c<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token keyword\">return<\/span> std<span class=\"token double-colon punctuation\">::<\/span>nullopt<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u65e0\u95ee\u5019\u8bed<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p><span class=\"token keyword\">int<\/span> <span class=\"token function\">main<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token keyword\">auto<\/span> greetingOpt <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">create_greeting<\/span><span class=\"token punctuation\">(<\/span><span class=\"token boolean\">true<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u68c0\u67e5\u5e76\u5b89\u5168\u8bbf\u95ee<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>greetingOpt<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token operator\">*<\/span>greetingOpt <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;, Sir\/Madam!&#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span>endl<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token keyword\">else<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;No greeting today.&#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span>endl<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u4f7f\u7528 value_or<\/span><br \/>\n    std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;Greeting: &#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> greetingOpt<span class=\"token punctuation\">.<\/span><span class=\"token function\">value_or<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;(none)&#034;<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span>endl<span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u5c1d\u8bd5\u8bbf\u95ee\u7a7a optional (\u5371\u9669!)<\/span><br \/>\n    <span class=\"token keyword\">auto<\/span> emptyOpt <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">create_greeting<\/span><span class=\"token punctuation\">(<\/span><span class=\"token boolean\">false<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>emptyOpt<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token operator\">*<\/span>greetingOpt <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;, Tom\/Jake!&#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span>endl<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token keyword\">else<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;No greeting today.&#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span>endl<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token keyword\">return<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p>\u8fd0\u884c\u7ed3\u679c&#xff1a; <img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2026\/02\/20260204094117-6983143db8506.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/><\/p>\n<h2>\u4e8c\u3001\u4ee3\u7801\u793a\u4f8b<\/h2>\n<p><span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;iostream&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;optional&gt;<\/span><\/span><\/p>\n<p><span class=\"token keyword\">int<\/span> <span class=\"token function\">main<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u521b\u5efa\u4e00\u4e2a std::optional&lt;int&gt; \u53d8\u91cf&#xff0c;\u521d\u59cb\u5316\u4e3a\u7a7a<\/span><br \/>\n    std<span class=\"token double-colon punctuation\">::<\/span>optional<span class=\"token operator\">&lt;<\/span><span class=\"token keyword\">int<\/span><span class=\"token operator\">&gt;<\/span> maybe_value<span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u68c0\u67e5\u503c\u662f\u5426\u5b58\u5728<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>maybe_value<span class=\"token punctuation\">.<\/span><span class=\"token function\">has_value<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;Value: &#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> maybe_value<span class=\"token punctuation\">.<\/span><span class=\"token function\">value<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span>endl<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span> <span class=\"token keyword\">else<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;No value present&#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span>endl<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u8bbe\u7f6e\u503c<\/span><br \/>\n    maybe_value <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">10<\/span><span class=\"token punctuation\">;<\/span>  <span class=\"token comment\">\/\/ \u73b0\u5728\u5305\u542b\u503c 10<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u518d\u6b21\u68c0\u67e5<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>maybe_value<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span>  <span class=\"token comment\">\/\/ \u4f7f\u7528\u5e03\u5c14\u4e0a\u4e0b\u6587\u68c0\u67e5<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;Value after assignment: &#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token operator\">*<\/span>maybe_value <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span>endl<span class=\"token punctuation\">;<\/span>  <span class=\"token comment\">\/\/ \u4f7f\u7528\u89e3\u5f15\u7528\u64cd\u4f5c\u7b26<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u91cd\u7f6e\u4e3a\u65e0\u503c<\/span><br \/>\n    maybe_value<span class=\"token punctuation\">.<\/span><span class=\"token function\">reset<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u5c1d\u8bd5\u8bbf\u95ee\u503c&#xff08;\u53ef\u80fd\u629b\u51fa std::bad_optional_access \u5f02\u5e38&#xff09;<\/span><br \/>\n    <span class=\"token keyword\">try<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;Value after reset: &#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> maybe_value<span class=\"token punctuation\">.<\/span><span class=\"token function\">value<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span>endl<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span> <span class=\"token keyword\">catch<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">const<\/span> std<span class=\"token double-colon punctuation\">::<\/span>bad_optional_access<span class=\"token operator\">&amp;<\/span> e<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;Error: &#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> e<span class=\"token punctuation\">.<\/span><span class=\"token function\">what<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span>endl<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token keyword\">return<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p>\u8fd0\u884c\u7ed3\u679c<\/p>\n<p>No value present<br \/>\nValue after assignment<span class=\"token operator\">:<\/span> <span class=\"token number\">10<\/span><br \/>\nValue after reset<span class=\"token operator\">:<\/span> Error<span class=\"token operator\">:<\/span> Bad optional access<\/p>\n<p>C<span class=\"token operator\">:<\/span>\\\\Users\\\\\u5f90\u9e4f\\\\Desktop\\\\\u65b0\u5efa\u6587\u4ef6\u5939\\\\Project1\\\\x64\\\\Debug\\\\Project1<span class=\"token punctuation\">.<\/span><span class=\"token function\">exe<\/span> <span class=\"token punctuation\">(<\/span>\u8fdb\u7a0b <span class=\"token number\">10380<\/span><span class=\"token punctuation\">)<\/span>\u5df2\u9000\u51fa&#xff0c;\u4ee3\u7801\u4e3a <span class=\"token number\">0<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token number\">0x0<\/span><span class=\"token punctuation\">)<\/span>\u3002<br \/>\n\u8981\u5728\u8c03\u8bd5\u505c\u6b62\u65f6\u81ea\u52a8\u5173\u95ed\u63a7\u5236\u53f0&#xff0c;\u8bf7\u542f\u7528\u201c\u5de5\u5177\u201d<span class=\"token operator\">-&gt;<\/span>\u201c\u9009\u9879\u201d<span class=\"token operator\">-&gt;<\/span>\u201c\u8c03\u8bd5\u201d<span class=\"token operator\">-&gt;<\/span>\u201c\u8c03\u8bd5\u505c\u6b62\u65f6\u81ea\u52a8\u5173\u95ed\u63a7\u5236\u53f0\u201d\u3002<br \/>\n\u6309\u4efb\u610f\u952e\u5173\u95ed\u6b64\u7a97\u53e3<span class=\"token punctuation\">.<\/span> <span class=\"token punctuation\">.<\/span> <span class=\"token punctuation\">.<\/span><\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2026\/02\/20260204094118-6983143e61fcb.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/><\/p>\n<p>\u4ee3\u7801\u89e3\u91ca<\/p>\n<li>\u58f0\u660e std::optional&#xff1a;\u5728\u4ee3\u7801\u5f00\u5934&#xff0c;\u6211\u4eec\u58f0\u660e\u4e86\u4e00\u4e2a std::optional&lt;int&gt; \u53d8\u91cf maybe_value&#xff0c;\u521d\u59cb\u5316\u4e3a\u7a7a&#xff08;\u4e0d\u5305\u542b\u503c&#xff09;\u3002<\/li>\n<li>\u68c0\u67e5\u503c\u5b58\u5728&#xff1a;\u4f7f\u7528 has_value() \u65b9\u6cd5\u6216\u76f4\u63a5\u4f7f\u7528 if (maybe_value) \u68c0\u67e5\u503c\u662f\u5426\u5b58\u5728\u3002\u7b2c\u4e00\u6b21\u68c0\u67e5\u65f6&#xff0c;\u53d8\u91cf\u4e3a\u7a7a&#xff0c;\u8f93\u51fa \u201cNo value present\u201d\u3002<\/li>\n<li>\u8bbe\u7f6e\u503c&#xff1a;\u901a\u8fc7\u8d4b\u503c\u64cd\u4f5c maybe_value &#061; 10&#xff0c;\u5c06\u503c\u8bbe\u7f6e\u4e3a 10\u3002<\/li>\n<li>\u8bbf\u95ee\u503c&#xff1a;\u4f7f\u7528 value() \u65b9\u6cd5\u6216\u89e3\u5f15\u7528\u64cd\u4f5c\u7b26 * \u83b7\u53d6\u503c\u3002\u5982\u679c\u503c\u5b58\u5728&#xff0c;\u8f93\u51fa\u5f53\u524d\u503c\u3002<\/li>\n<li>\u91cd\u7f6e\u503c&#xff1a;\u8c03\u7528 reset() \u65b9\u6cd5\u4f7f optional \u53d8\u91cf\u518d\u6b21\u4e3a\u7a7a\u3002<\/li>\n<li>\u5f02\u5e38\u5904\u7406&#xff1a;\u5f53\u5c1d\u8bd5\u8bbf\u95ee\u4e00\u4e2a\u7a7a\u7684 optional \u503c\u65f6&#xff0c;value() \u65b9\u6cd5\u4f1a\u629b\u51fa std::bad_optional_access \u5f02\u5e38\u3002\u6211\u4eec\u4f7f\u7528 try-catch \u5757\u6355\u83b7\u5e76\u5904\u7406\u8fd9\u4e2a\u5f02\u5e38\u3002<\/li>\n<p><img decoding=\"async\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2026\/02\/20260204094118-6983143ea8faf.png\" alt=\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\" \/><\/p>\n","protected":false},"excerpt":{"rendered":"<p>C std::optional\u8be6\u89e3-\u859b\u5b9a\u8c14\u7684\u201c\u76d2\u5b50\u201d&#xff01;\u4e00\u3001std::optional\u8be6\u89e31\u3001\u4ec0\u4e48\u662f std::optional&#xff1f;2\u3001\u4e3a\u4ec0\u4e48\u9700\u8981 std::optional&#xff1f;3\u3001\u6838\u5fc3\u64cd\u4f5c\u4e0e\u6210\u5458\u51fd\u65703.1 \u3001\u6784\u9020\u4e0e\u8d4b\u503c3.2\u3001 \u72b6\u6001\u68c0\u67e53.3\u3001 \u503c\u8bbf\u95ee3.4 \u3001\u4fee\u6539\u4e0e\u9500\u6bc13.5\u3001\u8bbf\u95ee\u5305\u542b\u7684\u503c (C23 \u65b0\u589e)4\u3001 \u5178\u578b\u4f7f\u7528\u573a\u666f5\u3001\u6ce8\u610f\u4e8b\u98796\u3001 \u793a\u4f8b\u4ee3\u7801\u4e8c\u3001\u4ee3\u7801\u793a\u4f8b\u4e00\u3001std::optional\u8be6\u89e3<br \/>\n1\u3001\u4ec0\u4e48\u662f std::optional<\/p>\n","protected":false},"author":2,"featured_media":71961,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[7566,55],"topic":[],"class_list":["post-71965","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-server","tag-optional","tag-c"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v20.3 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>C++ std::optional\u8be6\u89e3-\u859b\u5b9a\u8c14\u7684\u201c\u76d2\u5b50\u201d\uff01 - 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\u3001\u4fee\u6539\u4e0e\u9500\u6bc13.5\u3001\u8bbf\u95ee\u5305\u542b\u7684\u503c (C23 \u65b0\u589e)4\u3001 \u5178\u578b\u4f7f\u7528\u573a\u666f5\u3001\u6ce8\u610f\u4e8b\u98796\u3001 \u793a\u4f8b\u4ee3\u7801\u4e8c\u3001\u4ee3\u7801\u793a\u4f8b\u4e00\u3001std::optional\u8be6\u89e3 1\u3001\u4ec0\u4e48\u662f std::optional\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.wsisp.com\/helps\/71965.html\" \/>\n<meta property=\"og:site_name\" content=\"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\" \/>\n<meta property=\"article:published_time\" content=\"2026-02-04T09:41:19+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2026\/02\/20260204094115-6983143b364ad.png\" \/>\n<meta name=\"author\" content=\"admin\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u4f5c\u8005\" \/>\n\t<meta name=\"twitter:data1\" content=\"admin\" \/>\n\t<meta name=\"twitter:label2\" 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