C++ 模板重载调用

Question

我正在尝试实现一种执行模式，它接受任何函数并用它自己的函数执行它 conditions/preparations。不管这是一件有用的事情，它就是行不通。看来我无法访问 "Execute" 函数的模板重载（在 "main" 中调用）。

具体：为什么我不能调用Execute的重载模板函数？

这是完整的程序：

#include "stdafx.h"
#include <functional>

class TransparentFunctionWrapper
{
public:
    virtual void Execute(std::function<void()> executeFunction) = 0;

    template<class C>
    C Execute(std::function<C(void)> executeFunction) // template-overload of the abstract function which will implicitly call it
    {
        C ret;
        Execute( // calls the abstract function with a lambda function as parameter
        [ret, executeFunction](void) -> C       // lambda declaraction
        {                                       //
            ret = executeFunction;              // lambda body
        });                                     // 
        return ret;
    }
};

class ExampleExecutor : public TransparentFunctionWrapper
{
public:
    virtual void Execute(std::function<void()> executeFunction)
    {
        printf("executed before.");
        executeFunction();
        printf("executed after.");
    }
};

void DoStuff() {}
int ReturnStuff() { return -5; }

int main()
{
    ExampleExecutor executor;

    executor.Execute(DoStuff);
    int i = executor.Execute<int>(ReturnStuff);     // Why does this not work? ERROR: "type name is not allowed"

    getchar();
    return 0;
}

注：Visual Studio分

Execute<int>(ReturnStuff) // "int" is marked as Error: type name is not allowed

编译报错

"type 'int' unexpected"

感谢所有愿意帮助的人！

Answer 1

ExampleExecutor::Execute 没有覆盖 TransparentFunctionWrapper::Execute，它隐藏在 executor.Execute<int> 调用中。

您必须显式调用 TransparentFunctionWrapper::Execute，因为它被 ExampleExecutor::Execute 隐藏了。这是一种可行的方法：

int i = executor.TransparentFunctionWrapper::Execute<int>(ReturnStuff);

live example on coliru

C++ 模板重载调用

C++ template overload call

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