将成员函数传递给另一个对象的成员函数C ++ [英] Passing member function to another object's member function C++

问题描述

我有问题试图传递一个函数作为参数在另一个对象的函数。我很清楚，有很多类似的主题，但我不能得到他们的解决方案工作或不能理解他们。

I am having issues trying to pass a function as an argument in another object's function. I am well aware there are many similar topics but I either can't get their solution to work or can't understand them.

class foo
{
public:
    void func1(void (*Drawing)(void));

    template<class T>
    void func2(void (T::*Drawing)(void));
};

class bar
{
private:
    foo myFoo;
    void Drawing();
    void func3() {
        // Attempt 1
        myFoo.func1(Drawing);

        // Attempt 2
        myFoo.func2<bar>(&bar::Drawing);
    }
};

所以在我第一次尝试，我得到的错误，你不能转换 void（bar :: *）（void）到 void（*）（void），然后发现有正常的函数指针和成员函数指针。

So in my first attempt, I get the error where you can't convert void (bar::*)(void) to void (*)(void) of which I then found out there are normal function pointers and member function pointers.

尝试2是我的微弱尝试克服这个，但我现在得到未解决的外部...

Attempt 2 was my feeble attempt to overcome this but I get unresolved externals now...

那么，如何成功地将 Drawing（）成员函数传递给另一个对象的另一个函数？

So how can I successfully pass my Drawing() member function into another function from another object?

推荐答案

问题是你不能将 bar :: Drawing 视为 void（*）（void）函数，因为它是一个非静态方法，因此需要一个对象（这上下文将被使用）

The issue is that you cannot consider bar::Drawing as a void (*)(void) function since it's a non static method, which therefore required an object (the this context which will be used)

一个解决方案，假设c ++ 11对你来说，就是使用 std :: bind ，并轻松地修改你的foo定义：

A solution, assuming c++11 is ok for you, would be to use std::bind and to sligtly modify your foo definition:

class foo
{
    public:
    void func1(std::function<void(void)> Drawing)
    {
        Drawing(); // or do whatever you want with it
    }
};

那么你将能够做

void bar::func3() {
    myFoo.func1(std::bind(&bar::Drawing, this));
}

使大量潜在用途有效

int main()
{
    bar myBar;
    myBar.func3();

    foo myFoo;
    myFoo.func1([](){ printf("test\n"); });
    return 0;
}

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