C ++：初始化结构和设置函数指针 [英] C++: Initializing Struct and Setting Function Pointer

问题描述

我试图用函数指针初始化一个结构体，但是我有麻烦这样做，除非它是一个全局函数。以下代码工作原理：

I am trying to initialize a struct with a function pointer, however I am having trouble doing so unless it is done with a global function. The following code works:

float tester(float v){
    return 2.0f*v;
}

struct MyClass::Example{
    typedef float(*MyFunc)(float);

    MyFunc NameOfFunc;

    float DoSomething(float a){
        return NameOfFunc(a);
    }
};

struct Example e;
e.MyFunc = tester;

我的问题是每当我尝试用 tester 函数作为 MyClass 中的函数，代码不再有效。换句话说，我将测试器功能更改为：

My problem is whenever I try to do this with the tester function as a function in MyClass the code no longer works. In other words, I change the tester function to:

float MyClass::tester(float v){
    return 2.0f*v;
} 

任何和所有帮助，包括链接！我已经尝试谷歌搜索的问题，但不确定搜索什么（我已经尝试过类似类中的C ++结构函数指针初始化无效）

Any and all help is appreciated (including links)! I have tried googling around for the problem but am unsure what to search (I've tried things such as "C++ struct function pointer initialization in class" to no avail)

推荐答案

这是因为当你把函数作为类的成员，它将不再是类型 float（*）（float），而是 float（MyClass :: *）（float）。

This is because when you put the function as a member of the class, it will no longer be of the type float (*)(float), but rather, float (MyClass::*)(float).

href =http://en.cppreference.com/w/cpp/utility/functional/function =nofollow> std :: function 和 std :: mem_fn 来解决这些问题。

Look into std::function and std::mem_fn to solve these problems.

示例：

struct foo {
    float bar(int x, int y) {}
};

// This works
std::function<float(int, int)> func = std::mem_fn(&foo::bar);

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