{"id":781,"date":"2025-05-30T16:44:47","date_gmt":"2025-05-30T08:44:47","guid":{"rendered":"https:\/\/www.notown.top\/?p=781"},"modified":"2025-05-30T16:44:47","modified_gmt":"2025-05-30T08:44:47","slug":"%e8%a1%8c%e4%b8%ba%e5%8f%98%e5%8c%96%e6%a8%a1%e5%bc%8f%ef%bc%88%e5%91%bd%e4%bb%a4%e3%80%81%e8%ae%bf%e9%97%ae%e5%99%a8%ef%bc%89","status":"publish","type":"post","link":"https:\/\/www.notown.top\/?p=781","title":{"rendered":"\u884c\u4e3a\u53d8\u5316\u6a21\u5f0f\uff08\u547d\u4ee4\u3001\u8bbf\u95ee\u5668\uff09"},"content":{"rendered":"<blockquote><p>\n  \u5728\u7ec4\u4ef6\u7684\u6784\u5efa\u8fc7\u7a0b\u4e2d\uff0c\u7ec4\u4ef6\u884c\u4e3a\u7684\u53d8\u5316\u7ecf\u5e38\u5bfc\u81f4\u7ec4\u4ef6\u672c\u8eab\u5267\u70c8\u7684\u53d8\u5316\u3002\u201c\u884c\u4e3a\u53d8\u5316\u201d\u6a21\u5f0f\u5c06\u7ec4\u4ef6\u7684\u884c\u4e3a\u548c\u7ec4\u4ef6\u672c\u8eab\u8fdb\u884c\u89e3\u8026\uff0c\u4ece\u800c\u652f\u6301\u7ec4\u4ef6\u884c\u4e3a\u7684\u53d8\u5316\uff0c\u5b9e\u73b0\u4e24\u8005\u4e4b\u95f4\u7684\u677e\u8026\u5408\u3002<br \/>\n  \u5c5e\u4e8e\u201c\u884c\u4e3a\u53d8\u5316\u201d\u6a21\u5f0f\u7684\u6709Command\u548cVistor\n<\/p><\/blockquote>\n<h2>\u547d\u4ee4\u6a21\u5f0f\uff08Command\uff09<\/h2>\n<p>\u9002\u7528\u573a\u666f\uff1a<br \/>\n&#8211; \u5728\u8f6f\u4ef6\u6784\u5efa\u8fc7\u7a0b\u4e2d\uff0c\u201c\u884c\u4e3a\u8bf7\u6c42\u8005\u201d\u4e0e\u201c\u884c\u4e3a\u5b9e\u73b0\u8005\u201d\u901a\u5e38\u5448\u73b0\u4e00\u79cd\u201c\u7d27\u8026\u5408\u201d\u3002\u4f46\u5728\u67d0\u4e9b\u573a\u5408\u2014\u2014\u6bd4\u5982\u9700\u8981\u5bf9\u884c\u4e3a\u8fdb\u884c\u201c\u8bb0\u5f55\u3001\u64a4\u9500\uff08undo\/redo\uff09\u3001\u4e8b\u52a1\u201d\u7b49\u5904\u7406\uff0c\u8fd9\u79cd\u65e0\u6cd5\u62b5\u5fa1\u53d8\u5316\u7684\u7d27\u8026\u5408\u662f\u4e0d\u9002\u5408\u7684\u3002<br \/>\n&#8211; \u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u9700\u8981\u5c06\u201c\u884c\u4e3a\u8bf7\u6c42\u8005\u201d\u4e0e\u201c\u884c\u4e3a\u5b9e\u73b0\u8005\u201d\u89e3\u8026\uff0c\u5c06\u4e00\u7ec4\u884c\u4e3a\u62bd\u8c61\u4e3a\u5bf9\u8c61\uff0c\u53ef\u4ee5\u5b9e\u73b0\u4e8c\u8005\u4e4b\u95f4\u7684\u677e\u8026\u5408\u3002<\/p>\n<p>\u6a21\u5f0f\u5b9a\u4e49\uff1a<br \/>\n\u5c06\u4e00\u4e2a\u8bf7\u6c42\uff08\u884c\u4e3a\uff09\u5c01\u88c5\u4e3a\u4e00\u4e2a\u5bf9\u8c61\uff0c\u4ece\u800c\u4f7f\u4f60\u53ef\u7528\u4e0d\u540c\u7684\u8bf7\u6c42\u5bf9\u5ba2\u6237\u8fdb\u884c\u53c2\u6570\u5316\uff1b\u5bf9\u8bf7\u6c42\u6392\u961f\u6216\u8bb0\u5f55\u8bf7\u6c42\u65e5\u5fd7\uff0c\u4ee5\u53ca\u652f\u6301\u53ef\u64a4\u9500\u7684\u64cd\u4f5c\u3002<\/p>\n<pre><code class=\"language-cpp line-numbers\">class Command{\npublic:\n    virtual void execute() = 0;\n};\n\nclass ConcreteCommand01 : public Command{\n    string arg;\npublic:\n    ConcreteCommand01(const string &amp;a) : arg(a){}\n    void execute() override{\n        \/\/ \u6267\u884c\n    }\n};\n\nclass ConcreteCommand02 : public Command{\n    string arg;\npublic:\n    ConcreteCommand01(const string &amp;a) : arg(a){}\n    void execute() override{\n        \/\/ \u6267\u884c\n    }\n};\n\nclass MacroCommand : public Command{\n    vector&lt;Command*&gt; commands;\npublic:\n    void addCommand(Command *c) { commands.push_back(c); }\n    void execute() override{\n        for (auto &amp;c : commands){\n            c-&gt;execute();\n        }\n    }\n}\n\nint main(){\/\/ \u5176\u672c\u8d28\u5c31\u662f\u5c06\u4e00\u4e9b\u884c\u4e3a\uff08\u51fd\u6570\uff09\u5f53\u6210\u5bf9\u8c61\u7528\uff0c\u53ef\u4ee5\u968f\u610f\u7ec4\u5408\u3001\u5b58\u5728\u5bb9\u5668\u91cc\u3001\u8bb0\u5f55\u3002\n    ConcreteCommand01 command01(\"Command1\");\n    ConcreteCommand02 command02(\"Command2\");\n\n    MacroCommand macro;\n    macro.addCommand(&amp;command01);\n    macro.addCommand(&amp;command02);\n\n    macro.execute();\n\n    return 0;\n}\n\n<\/code><\/pre>\n<ul>\n<li>\u5176\u672c\u8d28\u5c31\u662f\u5c06\u4e00\u4e9b\u884c\u4e3a\uff08\u51fd\u6570\uff09\u5f53\u6210\u5bf9\u8c61\u7528\uff0c\u53ef\u4ee5\u968f\u610f\u7ec4\u5408\u3001\u5b58\u5728\u5bb9\u5668\u91cc\u3001\u8bb0\u5f55\u3002<\/li>\n<li>\u4f46\u662f\uff0c\u4e0a\u8ff0\u5b9e\u73b0\u662f\u4f7f\u7528\u865a\u51fd\u6570\uff0c\u9762\u5411\u5bf9\u8c61\u7684\u65b9\u5f0f\u89e3\u51b3\uff0c\u800cC++11\u540e\uff0c\u6709\u5f88\u591a\u65b9\u5f0f\u8d77\u5230\u7c7b\u4f3c\u4f5c\u7528\uff0c\u6bd4\u5982\u51fd\u6570\u5bf9\u8c61\uff08\u5728\u7c7b\u91cc\u91cd\u8f7d\u5706\u62ec\u53f7\u3001lambda\u3001std::function\u3001std::bind\uff09\uff0c\u51fd\u6570\u5bf9\u8c61\u53ef\u4ee5\u62e5\u6709\u81ea\u5df1\u7684\u6210\u5458\uff08\u6216\u67d0\u79cd\u65b9\u5f0f\u5b9e\u73b0\u72b6\u6001\u5b58\u50a8\uff09\u3002<\/li>\n<\/ul>\n<p>\u8981\u70b9\u603b\u7ed3\uff1a<br \/>\n&#8211; Command\u6a21\u5f0f\u6839\u672c\u76ee\u7684\u5728\u4e8e\u5c06\u201c\u884c\u4e3a\u8bf7\u6c42\u8005\u201d\u4e0e\u201c\u884c\u4e3a\u5b9e\u73b0\u8005\u201d\u89e3\u8026\uff0c\u5728\u9762\u5411\u5bf9\u8c61\u8bed\u8a00\u79cd\uff0c\u5e38\u89c1\u7684\u5b9e\u73b0\u624b\u6bb5\u662f\u201c\u5c06\u884c\u4e3a\u62bd\u8c61\u4e3a\u5bf9\u8c61\u201d<br \/>\n&#8211; \u5b9e\u73b0Command\u63a5\u53e3\u7684\u5177\u4f53\u547d\u4ee4\u5bf9\u8c61ConcreteCommand\u6709\u65f6\u5019\u6839\u636e\u9700\u8981\u53ef\u80fd\u4f1a\u4fdd\u5b58\u4e00\u4e9b\u989d\u5916\u7684\u72b6\u6001\u4fe1\u606f\u3002\u901a\u8fc7\u4f7f\u7528Composite\u6a21\u5f0f\uff0c\u53ef\u4ee5\u5c06\u591a\u4e2a\u201c\u547d\u4ee4\u201d\u5c01\u88c5\u4e3a\u4e00\u4e2a\u590d\u5408\u547d\u4ee4<\/p>\n<h2>\u8bbf\u95ee\u5668\uff08Visitor\uff09<\/h2>\n<p>\u4f7f\u7528\u573a\u666f\uff1a<br \/>\n\u5728\u8f6f\u4ef6\u6784\u5efa\u8fc7\u7a0b\u4e2d\uff0c\u7531\u4e8e\u9700\u6c42\u7684\u6539\u53d8\uff0c\u67d0\u4e9b\u7c7b\u5c42\u6b21\u7ed3\u6784\u4e2d\u5e38\u5e38\u9700\u8981\u589e\u52a0\u65b0\u7684\u884c\u4e3a\uff08\u65b9\u6cd5\uff09\uff0c\u5982\u679c\u76f4\u63a5\u5728\u57fa\u7c7b\u4e2d\u505a\u8fd9\u6837\u7684\u66f4\u6539\uff0c\u5c06\u4f1a\u7ed9\u5b50\u7c7b\u5e26\u6765\u5f88\u7e41\u91cd\u7684\u53d8\u66f4\u8d1f\u62c5\uff0c\u751a\u81f3\u7834\u574f\u539f\u6709\u7684\u8bbe\u8ba1<br \/>\n\u8bbf\u95ee\u5668\u6a21\u5f0f\u53ef\u4ee5\u5728\u4e0d\u66f4\u6539\u7c7b\u5c42\u6b21\u7ed3\u6784\u7684\u524d\u63d0\u4e0b\uff0c\u5728\u8fd0\u884c\u65f6\u6839\u636e\u9700\u8981\u900f\u660e\u5730\u4e3a\u7c7b\u5c42\u6b21\u7ed3\u6784\u4e0a\u7684\u5404\u4e2a\u7c7b\u52a8\u6001\u6dfb\u52a0\u65b0\u7684\u64cd\u4f5c\uff0c\u4ece\u800c\u907f\u514d\u4e0a\u8ff0\u95ee\u9898<\/p>\n<p>\u53cd\u9762\u6837\u4f8b\uff1a<\/p>\n<pre><code class=\"language-cpp line-numbers\">class Element{\npublic:\n    virtual void Func1() = 0;\n    virtual ~Element() {}\n};\n\nclass ElementA : public Element{\npublic:\n    void Func1() override{\n        \/\/ ...\n    } \n};\n\nclass ElementB : public Element{\npublic:\n    void Func1() override{\n        \/\/ ...\n    } \n};\n<\/code><\/pre>\n<p>\u5f53\u50cf\u4e0a\u9762\u8fd9\u6837\u5199\u65f6\uff0c\u5982\u679c\u57fa\u7c7bElement\u8981\u589e\u52a0\u4e00\u4e2a\u65b0\u7684\u884c\u4e3a\uff08\u51fd\u6570\uff09\uff0c\u90a3\u4e48\u6240\u6709\u7684\u5b50\u7c7b\u7684\u90fd\u8981\u8ddf\u7740\u589e\u52a0\uff0c\u5e76\u4e14\u662f\u5728\u539f\u4ee3\u7801\u7684\u57fa\u7840\u4e0a\u4fee\u6539\uff0c\u8fdd\u80cc\u4e86\u5bf9\u4fee\u6539\u5c01\u95ed\u7684\u539f\u5219\u3002<\/p>\n<p>\u6545\u6709\u4e0b\u8ff0\u5199\u6cd5<\/p>\n<pre><code class=\"language-cpp line-numbers\">class Visitor;\n\nclass Element{\npublic:\n    virtual void accept(Visitor &amp;vis) = 0;\n    virtual ~Element() {}\n};\n\nclass ElementA : public Element{\npublic:\n    void accept(Vistor &amp;vis) override {\n        vis.visitElementA(*this);\n    }\n};\n\nclass ElementB : public Element{\npublic:\n    void accept(Vistor &amp;vis) override {\n        vis.visitElementB(*this);\n    }\n};\n\nclass Visitor{\npublic:\n    virtual void visitElementA(ElementA &amp;elem) = 0;\n    virtual void visitElementB(ElementA &amp;elem) = 0;\n    virtual ~Visitor() {}\n};\n\nclass Visitor1 : public Visitor{ \/\/ \u884c\u4e3a1\uff0c\uff08\u6bd4\u5982\u4ed6\u53ef\u4ee5\u5b9e\u73b0\u7684\u662f\u6b65\u67aa\u5c04\u51fb\uff09\npublic:\n    void visitElementA(ElementA &amp;elem) override{\n        \/\/ ...\n    }\n    void visitElementB(ElementB &amp;elem) override{\n        \/\/ ...\n    }\n}\n\nclass Visitor2 : public Visitor{ \/\/ \u65b0\u884c\u4e3a2   \uff08\u53c8\u53ef\u4ee5\u65b0\u589e\u9730\u5f39\u5c04\u51fb\uff09\npublic:\n    void visitElementA(ElementA &amp;elem) override{\n        \/\/ ...\n    }\n    void visitElementB(ElementB &amp;elem) override{\n        \/\/ ...\n    }\n}\n\nint main(){\n    Visitor2 vis2;\n    ElementB *elementB;\n    \/\/ elementB.accept(vis2);\/\/ \u4e3aB\u8c03\u7528\u4e86\u884c\u4e3a2\u7684\u529f\u80fd\n    ElementA *elementA;\n\n    vector&lt;Element*&gt; arr{elementA, elementB};\n    for(auto &amp;ele:arr){\n        arr-&gt;accept(vis2); \/\/ \u4e3aA\u548cB\u90fd\u8c03\u7528\u4e86\u884c\u4e3a2\n    }\n\n    Visitor1 vis1;\n    for(auto &amp;ele:arr){\n        arr-&gt;accept(vis1); \/\/ \u4e3aA\u548cB\u90fd\u8c03\u7528\u4e86\u884c\u4e3a1\n    }\n\n    return 0;\n}\n\n<\/code><\/pre>\n<p><strong>\u4f46\u662f\u8be5\u6a21\u5f0f\u6700\u5927\u7684\u4e00\u4e2a\u7f3a\u70b9\u5c31\u662f\uff0cElement\u7684\u5b50\u7c7b\u6570\u91cf\u5e94\u8be5\u662f\u786e\u5b9a\u7684\uff0c\u4e0d\u7136Visitor\u7c7b\u7684\u865a\u51fd\u6570\u7684\u6570\u91cf\u5c31\u4f1a\u6839\u636eElement\u7684\u5b50\u7c7b\u6570\u91cf\u53d8\u5316\uff0c\u90a3\u4e48Visitor\u7684\u5b50\u7c7b\u4e5f\u4f1a\u53d8\u5316\uff0c\u8fdd\u80cc\u4e86\uff0c\u5f00\u95ed\u539f\u5219<\/strong><\/p>\n<p>\u8981\u70b9\u603b\u7ed3\uff1a<br \/>\n&#8211; Visitor\u6a21\u5f0f\u901a\u8fc7\u6240\u8c13\u53cc\u91cd\u5206\u53d1\uff08double dispatch\uff0caccept\u548cvisitElement\u90fd\u662f\u865a\u51fd\u6570\uff09\u6765\u5b9e\u73b0\u5728\u4e0d\u66f4\u6539\uff08\u4e0d\u6dfb\u52a0\u65b0\u7684\u64cd\u4f5c\u2014\u2014\u7f16\u8bd1\u65f6\uff09Element\u7c7b\u5c42\u6b21\u7ed3\u6784\u7684\u524d\u63d0\u4e0b\uff0c\u5728\u8fd0\u884c\u65f6\u900f\u660e\u5730\u4e3a\u7c7b\u5c42\u6b21\u7ed3\u6784\u7684\u5404\u4e2a\u7c7b\u52a8\u6001\u6dfb\u52a0\u65b0\u7684\u64cd\u4f5c\uff08\u652f\u6301\u53d8\u5316\uff09<br \/>\n&#8211; \u6240\u8c13\u53cc\u91cd\u5206\u53d1\uff0c\u5373Visitor\u6a21\u5f0f\u4e2d\u95f4\u5305\u62ec\u4e86\u4e24\u4e2a\u591a\u6001\u5206\u53d1\uff08accept\u548cvisitElement\uff09<br \/>\n&#8211; Visitor\u6a21\u5f0f\u7684\u6700\u5927\u7f3a\u70b9\u5728\u4e8e\u6269\u5c55\u7c7b\u5c42\u6b21\u7ed3\u6784\uff08\u589e\u6dfb\u65b0\u7684Element\u5b50\u7c7b\uff09\uff0c\u4f1a\u5bfc\u81f4Visitor\u7c7b\u7684\u6539\u53d8\u3002\u56e0\u6b64Visitor\u6a21\u5f0f\u9002\u7528\u4e8e\u201cElement\u5c42\u6b21\u7ed3\u6784\u7a33\u5b9a\uff0c\u800c\u5176\u4e2d\u64cd\u4f5c\u5374\u7ecf\u5e38\u9762\u4e34\u66f4\u6539<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5728\u7ec4\u4ef6\u7684\u6784\u5efa\u8fc7\u7a0b\u4e2d\uff0c\u7ec4\u4ef6\u884c\u4e3a\u7684\u53d8\u5316\u7ecf\u5e38\u5bfc\u81f4\u7ec4\u4ef6\u672c\u8eab\u5267\u70c8\u7684\u53d8\u5316\u3002\u201c\u884c\u4e3a\u53d8\u5316\u201d\u6a21\u5f0f\u5c06\u7ec4\u4ef6\u7684\u884c\u4e3a\u548c\u7ec4\u4ef6\u672c\u8eab\u8fdb\u884c\u89e3\u8026\uff0c&hellip;<a href=\"https:\/\/www.notown.top\/?p=781\" class=\"more-link\">Continue reading <span class=\"screen-reader-text\">\u884c\u4e3a\u53d8\u5316\u6a21\u5f0f\uff08\u547d\u4ee4\u3001\u8bbf\u95ee\u5668\uff09<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[22],"tags":[],"class_list":["post-781","post","type-post","status-publish","format-standard","hentry","category-22"],"_links":{"self":[{"href":"https:\/\/www.notown.top\/index.php?rest_route=\/wp\/v2\/posts\/781","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.notown.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.notown.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.notown.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.notown.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=781"}],"version-history":[{"count":1,"href":"https:\/\/www.notown.top\/index.php?rest_route=\/wp\/v2\/posts\/781\/revisions"}],"predecessor-version":[{"id":782,"href":"https:\/\/www.notown.top\/index.php?rest_route=\/wp\/v2\/posts\/781\/revisions\/782"}],"wp:attachment":[{"href":"https:\/\/www.notown.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=781"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.notown.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=781"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.notown.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=781"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}