{"id":2928,"date":"2019-02-11T10:11:34","date_gmt":"2019-02-11T01:11:34","guid":{"rendered":"https:\/\/www.chihayafuru.jp\/tech\/?p=2928"},"modified":"2019-02-11T10:15:20","modified_gmt":"2019-02-11T01:15:20","slug":"cpp-override%e3%81%97%e3%81%9f%e3%81%84%e3%83%a1%e3%83%b3%e3%83%90%e3%83%bc%e9%96%a2%e6%95%b0%e3%81%abvirtual%e3%82%92%e4%bb%98%e3%81%91%e5%bf%98%e3%82%8c%e3%82%8b%e3%81%a8%e3%81%a9%e3%81%86","status":"publish","type":"post","link":"https:\/\/www.chihayafuru.jp\/tech\/index.php\/archives\/2928","title":{"rendered":"[CPP] override\u3057\u305f\u3044\u30e1\u30f3\u30d0\u30fc\u95a2\u6570\u306bvirtual\u3092\u4ed8\u3051\u5fd8\u308c\u308b\u3068\u3069\u3046\u306a\u308b\u304b\uff1f"},"content":{"rendered":"

\u6d3e\u751f\u30af\u30e9\u30b9\u3067 override \u3059\u308b\u3053\u3068\u304c\u3067\u304d\u308b\u306e\u306f\u3001\u57fa\u5e95\u30af\u30e9\u30b9\u3067 virtual \u3092\u3064\u3051\u305f\u30e1\u30f3\u30d0\u30fc\u95a2\u6570\uff08\uff1d\u4eee\u60f3\u95a2\u6570\uff09\u3060\u3051\u3067\u3059\u3002\u3057\u304b\u3057\u3001\u3082\u3057 virtual\u3092\u3064\u3051\u3066\u3044\u306a\u3044\uff08\u3064\u3051\u308b\u306e\u3092\u5fd8\u308c\u305f\uff09\u30e1\u30f3\u30d0\u30fc\u95a2\u6570\uff08\uff1d\u975e\u4eee\u60f3\u95a2\u6570\uff09\u3092\u6d3e\u751f\u30af\u30e9\u30b9\u3067 override \u3057\u3088\u3046\u3068\u8a66\u307f\u308b\u3068\u4f55\u304c\u8d77\u3053\u308b\u3067\u3057\u3087\u3046\u304b\uff1f
\n<\/p>\n

1. virtual\u4fee\u98fe\u5b50\u3068override\u6307\u5b9a\u3092\u9069\u5207\u306b\u3064\u3051\u305f\u30b1\u30fc\u30b9<\/h2>\n
#include <iostream>\r\nusing namespace std;\r\n\r\nclass Base {\r\npublic:\r\n    virtual void say() { cout << \"Hello\" << endl; }\r\n};\r\n\r\nclass Derived : public Base {\r\npublic:\r\n    void say() override { cout << \"Bonjour\" << endl; }\r\n};\r\n\r\nint main(void){\r\n    Derived derivedObj;\r\n    Base* baseObj = &derivedObj;\r\n    \r\n    derivedObj.say(); \/\/ => bonjour\r\n    baseObj->say();   \/\/ => bonjour\r\n\r\n    return 0;\r\n}<\/pre>\n
virtual\u4fee\u98fe\u5b50\u3068override\u6307\u5b9a\u3092\u9069\u5207\u306b\u8a18\u8ff0\u3057\u3066\u3001\u4f5c\u6cd5\u901a\u308a\u306b\u4eee\u60f3\u95a2\u6570\u3068override\u3092\u5b9a\u7fa9\u3057\u3066\u3044\u307e\u3059\u3002
\n\u57fa\u5e95\u30af\u30e9\u30b9 Base \u306e\u30dd\u30a4\u30f3\u30bf\u7d4c\u7531\u3067\u30a2\u30af\u30bb\u30b9\u3057\u3066\u3082\u9069\u5207\u306b\u6d3e\u751f\u30af\u30e9\u30b9\u306e\u30e1\u30f3\u30d0\u30fc\u95a2\u6570\u304c\u547c\u3073\u51fa\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n
 <\/p>\n
2. virtual\u4fee\u98fe\u5b50\u3092\u5fd8\u308c\u305f\u30b1\u30fc\u30b9<\/h2>\n
\u3082\u3057\u4e0b\u8a18\u306e\u3088\u3046\u306b\u57fa\u5e95\u30af\u30e9\u30b9\u306e\u30e1\u30f3\u30d0\u30fc\u95a2\u6570\u306bvirtual\u3092\u4ed8\u3051\u5fd8\u308c\u308b\u3068\u30b3\u30f3\u30d1\u30a4\u30eb\u30a8\u30e9\u30fc\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n
#include <iostream>\r\nusing namespace std;\r\n\r\nclass Base {\r\npublic:\r\n    void say() { cout << \"Hello\" << endl; }\r\n};\r\n\r\nclass Derived : public Base {\r\npublic:\r\n    void say() override { cout << \"Bonjour\" << endl; } \/\/ => compile error\r\n};\r\n\r\nint main(void){\r\n    Derived derivedObj;\r\n    Base* baseObj = &derivedObj;\r\n    \r\n    derivedObj.say();\r\n    baseObj->say();\r\n\r\n    return 0;\r\n}<\/pre>\n
 <\/p>\n
3. virtual\u4fee\u98fe\u5b50\u3082override\u6307\u5b9a\u3082\u5fd8\u308c\u305f\u30b1\u30fc\u30b9<\/h2>\n
#include <iostream>\r\nusing namespace std;\r\n\r\nclass Base {\r\npublic:\r\n    void say() { cout << \"Hello\" << endl; }\r\n};\r\n\r\nclass Derived : public Base {\r\npublic:\r\n    void say() { cout << \"Bonjour\" << endl; }\r\n};\r\n\r\nint main(void){\r\n    Derived derivedObj;\r\n    Base* baseObj = &derivedObj;\r\n    \r\n    derivedObj.say(); \/\/ => bonjour\r\n    baseObj->say();   \/\/ => hello\r\n\r\n    return 0;\r\n}<\/pre>\n
\u4e0a\u8a18\u306e\u3088\u3046\u306b virtual \u3068 override \u306e\u4e21\u65b9\u306e\u8a18\u8ff0\u3092\u5fd8\u308c\u308b\u3068\u30b3\u30f3\u30d1\u30a4\u30e9\u30fc\u306f\u30a8\u30e9\u30fc\u3092\u767a\u3057\u307e\u305b\u3093\u3002\u3068\u3053\u308d\u304c\u5b9f\u969b\u306b\u5b9f\u884c\u3057\u3066\u307f\u308b\u3068\u30d7\u30ed\u30b0\u30e9\u30de\u306e\u610f\u306b\u53cd\u3057\u3066\uff08\uff1f\uff09\u3001Base\u30af\u30e9\u30b9\u306b\u30a2\u30c3\u30d7\u30ad\u30e3\u30b9\u30c8\u3057\u305f\u30dd\u30a4\u30f3\u30bf\u3092\u7d4c\u7531\u3057\u3066\u30a2\u30af\u30bb\u30b9\u3059\u308b\u3068\u57fa\u5e95\u30af\u30e9\u30b9\u306e\u30e1\u30f3\u30d0\u30fc\u95a2\u6570\u304c\u547c\u3073\u51fa\u3055\u308c\u3066\u3057\u307e\u3044\u307e\u3059\u3002\u3055\u3066\u4f55\u304c\u8d77\u3053\u3063\u3066\u3044\u308b\uff08\u51fa\u6765\u4e0a\u304c\u3063\u3066\u3044\u308b\uff09\u306e\u3067\u3057\u3087\u3046\u304b\uff1f\uff1f\uff1f<\/p>\n
 <\/p>\n
\u5927\u5207\u306a\u3053\u3068\u306f\u30b9\u30b3\u30c3\u30c8\u30fb\u30e1\u30a4\u30e4\u30fc\u30ba\u8457\u300eEffective C++ \u7b2c3\u7248\u300f\u306b\u66f8\u304b\u308c\u3066\u3044\u307e\u3057\u305f\u3002 \ud83d\ude00<\/p>\n
\uff13\uff13\u9805\u3000\u7d99\u627f\u3057\u305f\u540d\u524d\u3092\u96a0\u853d\u3057\u306a\u3044\u3088\u3046\u306b\u3057\u3088\u3046<\/p><\/blockquote>\n
 <\/p>\n
\u3053\u3053\u3067\u300c\u540d\u524d\u306e\u96a0\u853d\u300d\u3068\u300c\u518d\u5b9a\u7fa9\u300d\u306b\u3064\u3044\u3066\u8aac\u660e\u3057\u307e\u3059\u3002<\/p>\n
 <\/p>\n
4. \u30ed\u30fc\u30ab\u30eb\u5909\u6570\u306b\u3088\u308b\u30b0\u30ed\u30fc\u30d0\u30eb\u5909\u6570\u306e\u540d\u524d\u306e\u96a0\u853d<\/h2>\n
#include <iostream>\r\nusing namespace std;\r\n\r\nint x = 3;\r\n\r\nint main(void){\r\n    int x = 7;\r\n    printf(\"x = %d\\n\", x);      \/\/ x = 7\r\n    printf(\"x = %d\\n\", ::x);    \/\/ x = 3\r\n    return 0;\r\n}<\/pre>\n
\u30e1\u30a4\u30f3\u95a2\u6570\u306e\u4e2d\u3067\u30ed\u30fc\u30ab\u30eb\u5909\u6570 x<\/strong> \u3092\u518d\u5b9a\u7fa9\u3057\u305f\u3053\u3068\u3067\u30b0\u30ed\u30fc\u30d0\u30eb\u5909\u6570 x<\/strong> \u304c\u96a0\u3055\u308c\u3066\u3044\u307e\u3059\u3002
\nC\u8a00\u8a9e\u3067\u306f\u30b0\u30ed\u30fc\u30d0\u30eb\u5909\u6570\u306b\u30a2\u30af\u30bb\u30b9\u3059\u308b\u624b\u7acb\u3066\u306f\u3042\u308a\u307e\u305b\u3093\u304c\u3001C++\u3067\u306f\u30b9\u30b3\u30fc\u30d7\u89e3\u6c7a\u6f14\u7b97\u5b50 ::<\/code> \u3092\u4f7f\u3046\u3053\u3068\u3067\u3001main\u95a2\u6570\u306e\u4e2d\u304b\u3089\u30b0\u30ed\u30fc\u30d0\u30eb\u5909\u6570\u306b\u30a2\u30af\u30bb\u30b9\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n
\u4e0a\u8a18\u306e\u30b1\u30fc\u30b9\u3067\u306f\u30b0\u30ed\u30fc\u30d0\u30eb\u5909\u6570\u3068\u30ed\u30fc\u30ab\u30eb\u5909\u6570\u3067 x<\/strong> \u3068\u3044\u3046\u540d\u524d\u306e\u5909\u6570\u304c\u5404\u3005\u4e00\u3064\u305a\u3064\u5b58\u5728\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n
 <\/p>\n
5. \u57fa\u5e95\u30af\u30e9\u30b9\u306e\u30e1\u30f3\u30d0\u30fc\u5909\u6570\u3092\u6d3e\u751f\u30af\u30e9\u30b9\u3067\u518d\u5b9a\u7fa9<\/h2>\n
#include <iostream>\r\nusing namespace std;\r\n\r\nclass Base {\r\nprotected:\r\n    int x;\r\n    \r\npublic:\r\n    Base() { x = 3; };\r\n};\r\n\r\nclass Derived : Base {\r\nprotected:\r\n    double x;\r\n\r\npublic:\r\n    Derived() { x = 1.7; };\r\n    float get_derived_x() { return x; };    \/\/ => \"derived x = 1.7\"\r\n    int get_base_x() { return Base::x; };   \/\/ => \"   base x = 3\"\r\n};\r\n\r\n\r\nint main(void){\r\n    Derived obj;\r\n    \r\n    cout << \"derived x = \" << obj.get_derived_x() << endl;\r\n    cout << \"   base x = \" << obj.get_base_x() << endl;\r\n\r\n    return 0;\r\n}<\/pre>\n
\u4e0a\u8a18\u306e\u30b3\u30fc\u30c9\u3067\u306f\u57fa\u5e95\u30af\u30e9\u30b9\u3067\u5b9a\u7fa9\u3055\u308c\u305f\u30e1\u30f3\u30d0\u30fc\u5909\u6570 x<\/strong> \u3092\u6d3e\u751f\u30af\u30e9\u30b9\u3067\u518d\u5b9a\u7fa9\u3057\u3066\u3044\u307e\u3059\u3002\u57fa\u5e95\u30af\u30e9\u30b9\u3067\u306f\u6574\u6570\u578b(int)\u3067\u5b9a\u7fa9\u3057\u305f\u5909\u6570\u3092\u6d3e\u751f\u30af\u30e9\u30b9\u3067\u306f\u500d\u7cbe\u5ea6\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570(double)\u3067\u6562\u3048\u3066\u518d\u5b9a\u7fa9\u3057\u3066\u3044\u307e\u3059\u3002\u518d\u5b9a\u7fa9\u3067\u3059\u304b\u3089\u57fa\u5e95\u30af\u30e9\u30b9\u306e\u578b\u306b\u306f\u95a2\u4fc2\u306a\u304f\u3001\u6d3e\u751f\u30af\u30e9\u30b9\u3067\u306f\u7570\u306a\u308b\u578b\u3067\u5b9a\u7fa9\u3067\u304d\u307e\u3059\u3002
\n\u4e0a\u8a18\u306e\u30b3\u30fc\u30c9\u3067\u3082\u30b9\u30b3\u30fc\u30d7\u89e3\u6c7a\u6f14\u7b97\u5b50\u3092\u4f7f\u3063\u3066\u6d3e\u751f\u30af\u30e9\u30b9\u304b\u3089\u57fa\u5e95\u30af\u30e9\u30b9\u306e\u30e1\u30f3\u30d0\u30fc\u5909\u6570\u306b\u30a2\u30af\u30bb\u30b9\u3057\u3066\u3044\u307e\u3059\u3002\u57fa\u5e95\u30af\u30e9\u30b9\u306e\u30e1\u30f3\u30d0\u30fc\u5909\u6570 x<\/strong> \u3068 \u6d3e\u751f\u30af\u30e9\u30b9\u306e\u30e1\u30f3\u30d0\u30fc\u5909\u6570 x<\/strong> \u306f\u540d\u524d\u304c\u540c\u3058\u3060\u3051\u3067\u7570\u306a\u308b\u5b9f\u4f53\u3092\u6301\u3064\u3053\u3068\u304c\u308f\u304b\u308b\u3068\u601d\u3044\u307e\u3059\u3002<\/p>\n
 <\/p>\n
\u6700\u521d\u306e\u554f\u3044\u3078\u306e\u7b54\u3048\u3067\u3059\u3002
\n\u300coverride\u3057\u305f\u3044\u30e1\u30f3\u30d0\u30fc\u95a2\u6570\u306bvirtual\u3092\u4ed8\u3051\u5fd8\u308c\u308b\u3068\u3069\u3046\u306a\u308b\u304b\uff1f\u300d
\n\u7d99\u627f\u3057\u305f\u30e1\u30f3\u30d0\u30fc\u95a2\u6570\u306e\u540d\u524d\u3092\u96a0\u853d\u3057\u3066\u3001\u3042\u3089\u305f\u306a\u30e1\u30f3\u30d0\u30fc\u95a2\u6570\u3092\u518d\u5b9a\u7fa9\u3057\u307e\u3059\u3002override\u3067\u306f\u306a\u304f\u518d\u5b9a\u7fa9\u3067\u3042\u308b\u305f\u3081\u3001\u6d3e\u751f\u30af\u30e9\u30b9\uff08\u306e\u30dd\u30a4\u30f3\u30bf\uff09\u3092\u4ecb\u3057\u3066\u547c\u3073\u51fa\u3059\u3068\u6d3e\u751f\u30af\u30e9\u30b9\u3067\u518d\u5b9a\u7fa9\u3055\u308c\u305f\u30e1\u30f3\u30d0\u30fc\u95a2\u6570\u304c\u547c\u3073\u51fa\u3055\u308c\u3001\u30a2\u30c3\u30d7\u30ad\u30e3\u30b9\u30c8\u3057\u305f\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u30dd\u30a4\u30f3\u30bf\u3092\u4ecb\u3057\u3066\u547c\u3073\u51fa\u3057\u3092\u8a66\u307f\u308b\u3068\u3001\u57fa\u5e95\u30af\u30e9\u30b9\u306e\u30e1\u30f3\u30d0\u30fc\u95a2\u6570\u304c\u547c\u3073\u51fa\u3055\u308c\u307e\u3059\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u6d3e\u751f\u30af\u30e9\u30b9\u3067 override \u3059\u308b\u3053\u3068\u304c\u3067\u304d\u308b\u306e\u306f\u3001\u57fa\u5e95\u30af\u30e9\u30b9\u3067 virtual \u3092\u3064\u3051\u305f\u30e1\u30f3\u30d0\u30fc\u95a2\u6570\uff08\uff1d\u4eee\u60f3\u95a2\u6570\uff09\u3060\u3051\u3067\u3059\u3002\u3057\u304b\u3057\u3001\u3082\u3057 virtual\u3092\u3064\u3051\u3066\u3044\u306a\u3044\uff08\u3064\u3051\u308b\u306e\u3092\u5fd8\u308c\u305f\uff09\u30e1\u30f3\u30d0\u30fc\u95a2\u6570\uff08\uff1d\u975e\u4eee\u60f3\u95a2\u6570\uff09\u3092 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[84],"class_list":["post-2928","post","type-post","status-publish","format-standard","hentry","category-memo","tag-cpp"],"_links":{"self":[{"href":"https:\/\/www.chihayafuru.jp\/tech\/index.php\/wp-json\/wp\/v2\/posts\/2928","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.chihayafuru.jp\/tech\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.chihayafuru.jp\/tech\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.chihayafuru.jp\/tech\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.chihayafuru.jp\/tech\/index.php\/wp-json\/wp\/v2\/comments?post=2928"}],"version-history":[{"count":17,"href":"https:\/\/www.chihayafuru.jp\/tech\/index.php\/wp-json\/wp\/v2\/posts\/2928\/revisions"}],"predecessor-version":[{"id":2953,"href":"https:\/\/www.chihayafuru.jp\/tech\/index.php\/wp-json\/wp\/v2\/posts\/2928\/revisions\/2953"}],"wp:attachment":[{"href":"https:\/\/www.chihayafuru.jp\/tech\/index.php\/wp-json\/wp\/v2\/media?parent=2928"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.chihayafuru.jp\/tech\/index.php\/wp-json\/wp\/v2\/categories?post=2928"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.chihayafuru.jp\/tech\/index.php\/wp-json\/wp\/v2\/tags?post=2928"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}