{"id":6519,"date":"2022-06-28T17:42:51","date_gmt":"2022-06-28T09:42:51","guid":{"rendered":"https:\/\/yanjingang.com\/blog\/?p=6519"},"modified":"2022-06-28T17:46:56","modified_gmt":"2022-06-28T09:46:56","slug":"c-stdstatic_pointer_cast%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/yanjingang.com\/blog\/?p=6519","title":{"rendered":"C++ std::static_pointer_cast\u8be6\u89e3"},"content":{"rendered":"

\u4e00\u3001\u6982\u8ff0<\/h1>\n

static_pointer_cast\u4ece\u8868\u9762\u4e0a\u770b\u5c31\u662f\u9759\u6001\u6307\u9488\u7c7b\u578b\u8f6c\u6362\u3002\u7ec6\u7ec6\u770b\u6765\uff0c\u5e76\u4e0d\u662f\u90a3\u4e48\u7b80\u5355\uff0c\u6709\u4e00\u4e2a\u9690\u5f62\u7684\u9650\u5236\u6761\u4ef6\u3002\u9996\u5148\u8fd9\u4e2a\u662fc++11\u91cc\u7684\uff0c\u66f4\u8001\u7684\u7f16\u8bd1\u5668\u4e0d\u652f\u6301\uff0c\u5176\u6b21\u6307\u9488\u662fshared_ptr\u7c7b\u578b\u7684\uff0c\u5bf9\u4e8e\u666e\u901a\u6307\u9488\u662f\u65e0\u6548\u7684\u3002\u8fd8\u6709\u4e00\u822c\u53ea\u7528\u5728\u5b50\u7c7b\u7236\u7c7b\u7684\u7ee7\u627f\u5173\u7cfb\u4e2d\uff0c\u5f53\u5b50\u7c7b\u4e2d\u8981\u83b7\u53d6\u7236\u7c7b\u4e2d\u7684\u4e00\u4e9b\u5c5e\u6027\u65f6\uff0c\u6216\u5de5\u5382\u6a21\u5f0f\u7b49\u9700\u8981\u901a\u8fc7\u7236\u7c7b\u53c2\u6570\u63a5\u6536\u4e0d\u540c\u5b50\u7c7b\u5b9e\u4f8b\u7684\u573a\u666f(\u5f53\u7136\u4e86\u5b50\u7c7b\u901a\u8fc7\u591a\u6001\u62e5\u6709\u81ea\u5df1\u7684\u7236\u7c7b\u7ee7\u627f\u6765\u7684\u5c5e\u6027\u548c\u884c\u4e3a\uff0c\u4f46\u662f\u8fd8\u60f3\u77e5\u9053\u7236\u7c7b\u76f8\u5e94\u7684\u5c5e\u6027\u548c\u884c\u4e3a\uff0c\u8fd9\u65f6\uff0c\u5c06\u7236\u7c7b\u7684shared_ptr\u901a\u8fc7static_pointer_cast\u8f6c\u5316\u4e3a\u5b50\u7c7b\u7684shared_ptr\uff0c\u8fd9\u6837\u5c31\u53ef\u4ee5\u4f7f\u5f97\u5b50\u7c7b\u53ef\u4ee5\u8bbf\u95ee\u5230\u7236\u7c7b\u7684\u65b9\u6cd5)\u3002<\/p>\n

\u8fd9\u4e2a\u51fd\u6570\u8fd4\u56de\u7684\u662fshared_ptr\u7c7b\u578bsp\u7684\u4e00\u4efd\u5171\u4eab\u62f7\u8d1d\uff0c\u53ea\u4e0d\u8fc7\u5b83\u6307\u5411\u7684\u5bf9\u8c61\u7c7b\u578b\u4ece\u539f\u6765\u7684U\u53d8\u4e3aT\u3002<\/p>\n

\u5b9a\u4e49\uff1a<\/p>\n

\n
template<\/span> <<\/span>class<\/span> T<\/span>,<\/span> class<\/span> U<\/span>><\/span>\r\n  shared_ptr<\/span><<\/span>T<\/span>><\/span> static_pointer_cast<\/span> (<\/span>const<\/span> shared_ptr<\/span><<\/span>U<\/span>>&<\/span> sp<\/span>)<\/span> noexcept<\/span>;<\/span>\r\n<\/code><\/pre>\n<\/div>\n
\u89e3\u91ca\uff1a<\/p>\n
Returns a copy of\u00a0sp<\/i>\u00a0of the proper type with its\u00a0stored pointer<\/a>\u00a0casted statically from U* to T*.<\/p>\n
If\u00a0sp<\/i>\u00a0is not empty, the returned object shares ownership over\u00a0sp<\/i>‘s resources, increasing by one the\u00a0use count<\/a>.<\/p>\n
If\u00a0sp<\/i>\u00a0is empty, the returned object is an empty\u00a0shared_ptr<\/a>.<\/p>\n
\u4e8c\u3001\u5b9e\u6d4b<\/h1>\n
1.\u4f8b1<\/h3>\n
\n
\/\/ static_pointer_cast example\r\n<\/span>#include<\/span> <iostream><\/span>\r\n#include<\/span> <memory><\/span>\r\n\r\nstruct<\/span> A<\/span> {<\/span>\r\n  static<\/span> const<\/span> char<\/span>*<\/span> static_type<\/span>;<\/span>\r\n  const<\/span> char<\/span>*<\/span> dynamic_type<\/span>;<\/span>\r\n  A<\/span>()<\/span> {<\/span> dynamic_type<\/span> =<\/span> static_type<\/span>;<\/span> }<\/span>\r\n};<\/span>\r\nstruct<\/span> B<\/span>:<\/span> A<\/span> {<\/span>\r\n  static<\/span> const<\/span> char<\/span>*<\/span> static_type<\/span>;<\/span>\r\n  B<\/span>()<\/span> {<\/span> dynamic_type<\/span> =<\/span> static_type<\/span>;<\/span> }<\/span>\r\n};<\/span>\r\n\r\nconst<\/span> char<\/span>*<\/span> A<\/span>::<\/span>static_type<\/span> =<\/span> \"class A\"<\/span>;<\/span>\r\nconst<\/span> char<\/span>*<\/span> B<\/span>::<\/span>static_type<\/span> =<\/span> \"class B\"<\/span>;<\/span>\r\n\r\nint<\/span> main<\/span> ()<\/span> {<\/span>\r\n  std<\/span>::<\/span>shared_ptr<\/span><<\/span>A<\/span>><\/span> foo<\/span>;<\/span>\r\n  std<\/span>::<\/span>shared_ptr<\/span><<\/span>B<\/span>><\/span> bar<\/span>;<\/span>\r\n\r\n  foo<\/span> =<\/span> std<\/span>::<\/span>make_shared<\/span><<\/span>A<\/span>><\/span>();<\/span>\r\n\r\n  \/\/ cast of potentially incomplete object, but ok as a static cast:\r\n<\/span>  bar<\/span> =<\/span> std<\/span>::<\/span>static_pointer_cast<\/span><<\/span>B<\/span>><\/span>(<\/span>foo<\/span>);<\/span>\r\n\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"foo's static  type: \"<\/span> <<<\/span> foo<\/span>-><\/span>static_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"foo's dynamic type: \"<\/span> <<<\/span> foo<\/span>-><\/span>dynamic_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"bar's static  type: \"<\/span> <<<\/span> bar<\/span>-><\/span>static_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"bar's dynamic type: \"<\/span> <<<\/span> bar<\/span>-><\/span>dynamic_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n\r\n  return<\/span> 0<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n<\/div>\n
\u7ed3\u679c\uff1a<\/p>\n
\n
foo<\/span>'<\/span>s<\/span> static<\/span>  type<\/span>:<\/span> class<\/span> A<\/span>\r\nfoo<\/span>'<\/span>s<\/span> dynamic<\/span> type<\/span>:<\/span> class<\/span> A<\/span>\r\nbar<\/span>'<\/span>s<\/span> static<\/span>  type<\/span>:<\/span> class<\/span> B<\/span>\r\nbar<\/span>'<\/span>s<\/span> dynamic<\/span> type<\/span>:<\/span> class<\/span> A<\/span>\r\n<\/code><\/pre>\n<\/div>\n
\u4e0d\u7528std::static_pointer_cast<\/p>\n
\n
\/\/ static_pointer_cast example\r\n<\/span>#include<\/span> <iostream><\/span>\r\n#include<\/span> <memory><\/span>\r\n\r\nstruct<\/span> A<\/span> {<\/span>\r\n  static<\/span> const<\/span> char<\/span>*<\/span> static_type<\/span>;<\/span>\r\n  const<\/span> char<\/span>*<\/span> dynamic_type<\/span>;<\/span>\r\n  A<\/span>()<\/span> {<\/span> dynamic_type<\/span> =<\/span> static_type<\/span>;<\/span> }<\/span>\r\n};<\/span>\r\nstruct<\/span> B<\/span>:<\/span> A<\/span> {<\/span>\r\n  static<\/span> const<\/span> char<\/span>*<\/span> static_type<\/span>;<\/span>\r\n  B<\/span>()<\/span> {<\/span> dynamic_type<\/span> =<\/span> static_type<\/span>;<\/span> }<\/span>\r\n};<\/span>\r\n\r\nconst<\/span> char<\/span>*<\/span> A<\/span>::<\/span>static_type<\/span> =<\/span> \"class A\"<\/span>;<\/span>\r\nconst<\/span> char<\/span>*<\/span> B<\/span>::<\/span>static_type<\/span> =<\/span> \"class B\"<\/span>;<\/span>\r\n\r\nint<\/span> main<\/span> ()<\/span> {<\/span>\r\n  std<\/span>::<\/span>shared_ptr<\/span><<\/span>A<\/span>><\/span> foo<\/span>;<\/span>\r\n  std<\/span>::<\/span>shared_ptr<\/span><<\/span>B<\/span>><\/span> bar<\/span>;<\/span>\r\n\r\n  foo<\/span> =<\/span> std<\/span>::<\/span>make_shared<\/span><<\/span>A<\/span>><\/span>();<\/span>\r\n\r\n  \/\/ cast of potentially incomplete object, but ok as a static cast:\r\n<\/span>  bar<\/span> =<\/span> std<\/span>::<\/span>make_shared<\/span><<\/span>B<\/span>><\/span>();<\/span>\r\n  \/\/bar = std::static_pointer_cast<B>(foo);\r\n<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"foo's static  type: \"<\/span> <<<\/span> foo<\/span>-><\/span>static_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"foo's dynamic type: \"<\/span> <<<\/span> foo<\/span>-><\/span>dynamic_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"bar's static  type: \"<\/span> <<<\/span> bar<\/span>-><\/span>static_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"bar's dynamic type: \"<\/span> <<<\/span> bar<\/span>-><\/span>dynamic_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n\r\n  return<\/span> 0<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n<\/div>\n
\u7ed3\u679c<\/p>\n
\n
foo<\/span>'<\/span>s<\/span> static<\/span>  type<\/span>:<\/span> class<\/span> A<\/span>\r\nfoo<\/span>'<\/span>s<\/span> dynamic<\/span> type<\/span>:<\/span> class<\/span> A<\/span>\r\nbar<\/span>'<\/span>s<\/span> static<\/span>  type<\/span>:<\/span> class<\/span> B<\/span>\r\nbar<\/span>'<\/span>s<\/span> dynamic<\/span> type<\/span>:<\/span> class<\/span> B<\/span>\r\n<\/code><\/pre>\n<\/div>\n
\u4e8b\u5b9e\u4e0a\uff0c\u5f53\u5728\u8c03\u7528\u4e0b\u9762\u8fd9\u53e5\u8bdd\u65f6\uff0cB\u5bf9\u8c61\u6ca1\u6709\u88ab\u6784\u9020(\u5206\u914d\u5185\u5b58)\uff0cbar\u662f\u6307\u5411foo\u5bf9\u8c61\u7684\u3002<\/p>\n
\n
\/\/ static_pointer_cast example\r\n<\/span>#include<\/span> <iostream><\/span>\r\n#include<\/span> <memory><\/span>\r\n\r\nstruct<\/span> A<\/span> {<\/span>\r\n  static<\/span> const<\/span> char<\/span>*<\/span> static_type<\/span>;<\/span>\r\n  const<\/span> char<\/span>*<\/span> dynamic_type<\/span>;<\/span>\r\n  A<\/span>()<\/span> {<\/span> std<\/span>::<\/span>cout<\/span> <<<\/span> \"construct A \"<\/span> <<<\/span> std<\/span>::<\/span>endl<\/span>;<\/span> dynamic_type<\/span> =<\/span> static_type<\/span>;<\/span> }<\/span>\r\n};<\/span>\r\nstruct<\/span> B<\/span>:<\/span> A<\/span> {<\/span>\r\n  static<\/span> const<\/span> char<\/span>*<\/span> static_type<\/span>;<\/span>\r\n B<\/span>()<\/span> {<\/span> std<\/span>::<\/span>cout<\/span> <<<\/span> \"construct B \"<\/span> <<<\/span> std<\/span>::<\/span>endl<\/span>;<\/span> dynamic_type<\/span> =<\/span> static_type<\/span>;<\/span> }<\/span>\r\n};<\/span>\r\n\r\nconst<\/span> char<\/span>*<\/span> A<\/span>::<\/span>static_type<\/span> =<\/span> \"class A\"<\/span>;<\/span>\r\nconst<\/span> char<\/span>*<\/span> B<\/span>::<\/span>static_type<\/span> =<\/span> \"class B\"<\/span>;<\/span>\r\nint<\/span> main<\/span> ()<\/span> {<\/span>\r\n  std<\/span>::<\/span>shared_ptr<\/span><<\/span>A<\/span>><\/span> foo<\/span>;<\/span>\r\n  std<\/span>::<\/span>shared_ptr<\/span><<\/span>B<\/span>><\/span> bar<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"foo's static  type: \"<\/span> <<<\/span> foo<\/span>-><\/span>static_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"bar's static  type: \"<\/span> <<<\/span> bar<\/span>-><\/span>static_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  foo<\/span> =<\/span> std<\/span>::<\/span>make_shared<\/span><<\/span>A<\/span>><\/span>();<\/span>\r\n  \/\/ cast of potentially incomplete object, but ok as a static cast:\r\n<\/span>  bar<\/span> =<\/span> std<\/span>::<\/span>static_pointer_cast<\/span><<\/span>B<\/span>><\/span>(<\/span>foo<\/span>);<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"foo's static  type: \"<\/span> <<<\/span> foo<\/span>-><\/span>static_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"foo's dynamic type: \"<\/span> <<<\/span> foo<\/span>-><\/span>dynamic_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"bar's static  type: \"<\/span> <<<\/span> bar<\/span>-><\/span>static_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"bar's dynamic type: \"<\/span> <<<\/span> bar<\/span>-><\/span>dynamic_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n\r\n  return<\/span> 0<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n<\/div>\n
\u8f93\u51fa\uff1a<\/p>\n
\n
foo<\/span>'<\/span>s<\/span> static<\/span>  type<\/span>:<\/span> class<\/span> A<\/span>\r\nbar<\/span>'<\/span>s<\/span> static<\/span>  type<\/span>:<\/span> class<\/span> B<\/span>\r\nconstruct<\/span> A<\/span> \r\nfoo<\/span>'<\/span>s<\/span> static<\/span>  type<\/span>:<\/span> class<\/span> A<\/span>\r\nfoo<\/span>'<\/span>s<\/span> dynamic<\/span> type<\/span>:<\/span> class<\/span> A<\/span>\r\nbar<\/span>'<\/span>s<\/span> static<\/span>  type<\/span>:<\/span> class<\/span> B<\/span>\r\nbar<\/span>'<\/span>s<\/span> dynamic<\/span> type<\/span>:<\/span> class<\/span> A<\/span>\r\n<\/code><\/pre>\n<\/div>\n
2.\u4f8b2<\/h3>\n
\u518d\u770b\u4ee5\u4e0b\u8f6c\u53d8\u8fc7\u7a0b<\/p>\n
\n
\/\/ static_pointer_cast example\r\n<\/span>#include<\/span> <iostream><\/span>\r\n#include<\/span> <memory><\/span>\r\n\r\nstruct<\/span> A<\/span> {<\/span>\r\n  static<\/span> const<\/span> char<\/span>*<\/span> static_type<\/span>;<\/span>\r\n  const<\/span> char<\/span>*<\/span> dynamic_type<\/span>;<\/span>\r\n  A<\/span>()<\/span> {<\/span> std<\/span>::<\/span>cout<\/span> <<<\/span> \"construct A \"<\/span> <<<\/span> std<\/span>::<\/span>endl<\/span>;<\/span> dynamic_type<\/span> =<\/span> static_type<\/span>;<\/span> }<\/span>\r\n};<\/span>\r\nstruct<\/span> B<\/span>:<\/span> A<\/span> {<\/span>\r\n  static<\/span> const<\/span> char<\/span>*<\/span> static_type<\/span>;<\/span>\r\n B<\/span>()<\/span> {<\/span> std<\/span>::<\/span>cout<\/span> <<<\/span> \"construct B \"<\/span> <<<\/span> std<\/span>::<\/span>endl<\/span>;<\/span> dynamic_type<\/span> =<\/span> static_type<\/span>;<\/span> }<\/span>\r\n};<\/span>\r\n\r\nconst<\/span> char<\/span>*<\/span> A<\/span>::<\/span>static_type<\/span> =<\/span> \"class A\"<\/span>;<\/span>\r\nconst<\/span> char<\/span>*<\/span> B<\/span>::<\/span>static_type<\/span> =<\/span> \"class B\"<\/span>;<\/span>\r\nint<\/span> main<\/span> ()<\/span> {<\/span>\r\n  std<\/span>::<\/span>shared_ptr<\/span><<\/span>A<\/span>><\/span> foo<\/span>;<\/span>\r\n  std<\/span>::<\/span>shared_ptr<\/span><<\/span>B<\/span>><\/span> bar<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"foo's static  type: \"<\/span> <<<\/span> foo<\/span>-><\/span>static_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"bar's static  type: \"<\/span> <<<\/span> bar<\/span>-><\/span>static_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  foo<\/span> =<\/span> std<\/span>::<\/span>make_shared<\/span><<\/span>A<\/span>><\/span>();<\/span>\r\n  bar<\/span> =<\/span> std<\/span>::<\/span>make_shared<\/span><<\/span>B<\/span>><\/span>();<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"bar's static  type: \"<\/span> <<<\/span> bar<\/span>-><\/span>static_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"bar's dynamic type: \"<\/span> <<<\/span> bar<\/span>-><\/span>dynamic_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  \/\/ cast of potentially incomplete object, but ok as a static cast:\r\n<\/span>  bar<\/span> =<\/span> std<\/span>::<\/span>static_pointer_cast<\/span><<\/span>B<\/span>><\/span>(<\/span>foo<\/span>);<\/span>\r\n\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"foo's static  type: \"<\/span> <<<\/span> foo<\/span>-><\/span>static_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"foo's dynamic type: \"<\/span> <<<\/span> foo<\/span>-><\/span>dynamic_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"bar's static  type: \"<\/span> <<<\/span> bar<\/span>-><\/span>static_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n  std<\/span>::<\/span>cout<\/span> <<<\/span> \"bar's dynamic type: \"<\/span> <<<\/span> bar<\/span>-><\/span>dynamic_type<\/span> <<<\/span> '\\n'<\/span>;<\/span>\r\n\r\n  return<\/span> 0<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n<\/div>\n
\u8f93\u51fa<\/p>\n
\n
foo<\/span>'<\/span>s<\/span> static<\/span>  type<\/span>:<\/span> class<\/span> A<\/span>\r\nbar<\/span>'<\/span>s<\/span> static<\/span>  type<\/span>:<\/span> class<\/span> B<\/span>\r\nconstruct<\/span> A<\/span> #\u6784\u9020<\/span>A<\/span>\r\nconstruct<\/span> A<\/span> #<\/span>B\u7ee7\u627fA<\/span>,<\/span>\u6784\u9020<\/span>B\u65f6\u5148\u6784\u9020A<\/span>\r\nconstruct<\/span> B<\/span> \r\nbar<\/span>'<\/span>s<\/span> static<\/span>  type<\/span>:<\/span> class<\/span> B<\/span>\r\nbar<\/span>'<\/span>s<\/span> dynamic<\/span> type<\/span>:<\/span> class<\/span> B<\/span> #<\/span>B\u6784\u9020\u540e\u5b83\u7684dynamic<\/span> type\u4e3aclass<\/span> B<\/span>\r\nfoo<\/span>'<\/span>s<\/span> static<\/span>  type<\/span>:<\/span> class<\/span> A<\/span>\r\nfoo<\/span>'<\/span>s<\/span> dynamic<\/span> type<\/span>:<\/span> class<\/span> A<\/span>\r\nbar<\/span>'<\/span>s<\/span> static<\/span>  type<\/span>:<\/span> class<\/span> B<\/span>\r\nbar<\/span>'<\/span>s<\/span> dynamic<\/span> type<\/span>:<\/span> class<\/span> A<\/span> #\u4f7f\u7528<\/span>static_pointer_cast\u8f6c\u6362\u540edymamic<\/span> type\u53d8\u4e3aclass<\/span> A<\/span><\/code><\/pre>\n<\/div>\n
\u4e09\u3001\u7ed3\u8bba<\/h1>\n
\u901a\u8fc7\u5404\u79cd\u6d4b\u8bd5\uff0c\u57fa\u672c\u53ef\u4ee5\u770b\u51fa\u6765\uff0cstatic_pointer_cast\u53ef\u4ee5\u5c06\u7236\u7c7b\u53c2\u6570\u5f3a\u5236\u8f6c\u6362\u4e3a\u5b50\u7c7b\u7c7b\u578b\uff0c\u5e76\u7ee7\u627f\u5b50\u7c7b\u7684static\u5c5e\u6027\u3002<\/span>\u5b9e\u9645\u5e94\u7528\u4e2d\uff0c\u53ef\u4ee5\u5c06\u65b9\u6cd5\u53c2\u6570\u5b9a\u4e49\u4e3a\u7236\u7c7b\u578b\uff0c\u4f46\u5b9e\u9645\u4f20\u5165\u5b50\u7c7b\u578b\uff0c\u901a\u8fc7static_pointer_cast\u83b7\u5f97\u5b50\u7c7b\u7279\u6709\u7684\u65b9\u6cd5\u548cstatic\u5c5e\u6027\uff0c\u7c7b\u4f3c\u4e0b\u65b9\u7684\u5e94\u7528\u573a\u666f\u3002<\/span><\/p>\n
struct ContextTest : public ContextBase {\r\n    ~ContextTest() {\r\n        PINFO << \"[TaskFlow] Done! Context content is: \" << content;\r\n    }\r\n    std::string content;\r\n};\r\nauto taskflow_ = std::make_shared<TaskFlow>(true);\r\nauto taskA = taskflow->CreateSubTask([](std::shared_ptr<ContextBase<\/span>>& c<\/span>){\r\n        static int a_cnt = 0;\r\n        auto ctx = std::static_pointer_cast<ContextTest>(c);<\/span>    \/\/ \u5c06ContextBase\u53c2\u6570c\u5f3a\u5236\u8f6c\u6362\u4e3a\u5b50\u7c7bContextTest\u7c7b\u578b\uff0c\u5e76\u7ee7\u627fContextTest\u7684static\u5c5e\u6027\r\n        ctx->content += \"task A done in round \" << std::to_string(a_cnt) << \"; \" ;\r\n });\r\n\r\nauto ctx = std::make_shared<ContextTest<\/span>>(); \r\nctx->content = \"Round \" + std::to_string(i) + \" : \"; \r\ntaskflow->Start(ctx<\/span>);<\/code><\/pre>\n
 <\/p>\n
22.6.28<\/p>\n","protected":false},"excerpt":{"rendered":"
\u4e00\u3001\u6982\u8ff0 static_pointer_cast\u4ece\u8868\u9762\u4e0a\u770b\u5c31\u662f\u9759\u6001\u6307\u9488\u7c7b\u578b\u8f6c\u6362\u3002\u7ec6\u7ec6\u770b\u6765\uff0c\u5e76\u4e0d\u662f\u90a3\u4e48\u7b80\u5355\uff0c\u6709\u4e00 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[1027],"tags":[1214],"_links":{"self":[{"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/6519"}],"collection":[{"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=6519"}],"version-history":[{"count":3,"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/6519\/revisions"}],"predecessor-version":[{"id":6524,"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/6519\/revisions\/6524"}],"wp:attachment":[{"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6519"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6519"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6519"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}