如何在綁定函數中「自動發送」調用對象的實例？

Question

Here's my code：

#include <iostream> 
#include <functional> 
#include <vector> 

class Voice 
{ 
public: 
    double mVoiceValue = 0.0; 
    std::function<double(Voice &, double)> mTargetFunction; 

    Voice(std::function<double(Voice &, double)> targetFunction) : mTargetFunction(targetFunction) { } 
    ~Voice() { }  

private: 
}; 

class Osc 
{ 
public: 
    double mOscValue = 1.0; 

    Osc() { } 
    ~Osc() { } 

    double Modulate(Voice &voice, double value) { 
     return mOscValue * voice.mVoiceValue * value; 
    } 

private: 
}; 

int main() 
{ 
    Osc *osc = new Osc(); 
    Voice voice1(std::bind(&Osc::Modulate, osc, std::placeholders::_1, std::placeholders::_2)); 
    Voice voice2(std::bind(&Osc::Modulate, osc, std::placeholders::_1, std::placeholders::_2)); 

    voice1.mVoiceValue = 1.0; 
    voice2.mVoiceValue = 2.0; 
    std::cout << "value: " << voice1.mTargetFunction(voice1, 10.0) << std::endl; 
    std::cout << "value: " << voice2.mTargetFunction(voice2, 100.0) << std::endl; 
} 

我想非傳遞voice1/voice2實例（即本身）到調用bind函數。因爲我想直接發送該實例，因爲它與調用對象相同。

如何以這種方式進行綁定？

即它必須返回相同的結果調用：

std::cout << "value: " << voice1.mTargetFunction(10.0) << std::endl; 
std::cout << "value: " << voice2.mTargetFunction(100.0) << std::endl; 

Answer 1

如果它的好了Voice構造方法來參數（在Osc對象和成員函數指針）可以解決這個問題是這樣的：

class Voice 
{ 
public: 
    double mVoiceValue = 0.0; 
    std::function<double(double)> mTargetFunction; 

    template<typename T, typename F> 
    Voice(T& targetObject, F&& targetFunction) 
     : mTargetFunction(std::bind(targetFunction, targetObject, std::ref(*this), std::placeholders::_1)) { } 
    ~Voice() { } 
}; 

class Osc 
{ 
public: 
    double mOscValue = 1.0; 

    Osc() { } 
    ~Osc() { } 

    double Modulate(Voice &voice, double value) { 
     return mOscValue * voice.mVoiceValue * value; 
    } 
}; 

... 

Osc osc; 
Voice voice1(osc, &Osc::Modulate); 
Voice voice2(osc, &Osc::Modulate); 

voice1.mVoiceValue = 1.0; 
voice2.mVoiceValue = 2.0; 
std::cout << "value: " << voice1.mTargetFunction(10.0) << std::endl; 
std::cout << "value: " << voice2.mTargetFunction(100.0) << std::endl; 

這裏最重要的一點是std::ref爲Voice參數的用法。

如果它始終是要被稱爲Modulate成員函數，那麼Voice構造不必帶指針的成員函數作爲參數，然後使用&T::Modulate在調用std::bind。