将成员函数指针分配为来自另一个函数的回调 [英] Assign a member function pointer as a callback from another function

问题描述

我有一个类A，该类具有用于回调的函数指针。默认值是类A的一些函数指针，但我想分配类B的一个函数指针。我尝试了 std :: function 和 std： ：bind ，但不起作用。我尝试使用此答案，但没有

I have a class A that has a function pointer for a callback. The default values are some function pointer from class A but I want to assign a function pointer from class B. I tried std::function and std::bind but it is not working. I tried to use this answer but without success.

代码为：

#include <iostream>
#include <string>
#include <functional>

class A{
public:
    typedef void(*action)() ;

    A( std::function<void()> a  = nullptr)
    {
        if(a)
            m_Func = a; 
        else
            m_Func = std::bind( (this->*(this->dummyFunction))() );
    }
    std::function<void(void)> m_Func;
    void dummyFunction(void){std::cout<<"dummy function\n" <<std::endl;}
};

class B{
public:
    std::function<void()> m_Bfunc(){ std::cout << "class B func\n" <<std::endl;}
};

int main()
{
  B b;
  A a(b.m_Bfunc);
  a.m_Func();
}

我希望函数 m_Bfunc 运行。

推荐答案

似乎要：

class A{
public:
    A(std::function<void()> a = nullptr)
    {
        if(a)
            m_Func = a; 
        else
            m_Func = [this](){ dummyFunction(); };
    }
    std::function<void()> m_Func;
    void dummyFunction(){std::cout<<"dummy function\n" <<std::endl;}
};

class B{
public:
    void func(){ std::cout << "class B func\n" <<std::endl;}
};

int main()
{
  B b;
  A a([&](){b.func(); });
  a.m_Func();
}

演示

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