我在哪里绑定它是错误的？

Question

这是我的attempt

#include <iostream>
#include <functional>

class Voice;

class EnvelopeMultiPoints
{
public:
    std::function<double(Voice &, double)> mCallback;

    void SetupModulation(std::function<double(Voice &, double)> callback, int paramID) {  
        mCallback = callback;
    }
};

class Voice
{
public:
    EnvelopeMultiPoints mEnvelopeMultiPoints;
};

class VoiceManager
{
public:
    Voice mVoices[16];

    inline void UpdateVoices(std::function<void(Voice &)> callback) {
        for (int i = 0; i < 16; i++) {
            callback(mVoices[i]);
        }
    }
    static void SetupEnvelopeMultiPointsModulation(Voice &voice, std::function<double(Voice &, double)> callback, int paramID) {
        voice.mEnvelopeMultiPoints.SetupModulation(callback, paramID);
    }
};

class Oscillator
{
public:
    double ModulatePitch(Voice &voice, double currentValue) { 
        // somethings with voice
        return currentValue * 10.0; 
    }
};

int main()
{    
    VoiceManager voiceManager;
    Oscillator *pOscillator = new Oscillator();

    int param = 100;
    auto callback = std::bind(&Oscillator::ModulatePitch, pOscillator, std::placeholders::_1, std::placeholders::_2);
    voiceManager.UpdateVoices(std::bind(&VoiceManager::SetupEnvelopeMultiPointsModulation, std::placeholders::_1, callback, param));    

    Voice voice = voiceManager.mVoices[0];
    std::cout << voice.mEnvelopeMultiPoints.mCallback(voice, 1.0) << std::endl;

    delete pOscillator;
}

我创建了一种Voice Updater "basic“迭代器，稍后我可以传递任何类型的函数。它迭代所有的声音，并传递迭代所需的函数。

但是似乎我在绑定Oscillator::ModulatePitch函数来传递给更新器上是错误的？

我哪里错了？

Answer 1

正如pergy在其评论中所写的那样，如果你使用std::function<double(Voice &, double)> callback = ...而不是auto，它就可以工作。原因是它强制从bind对象转换为std::function。

如果你这样做了

auto callback1 = std::bind(&Oscillator::ModulatePitch, pOscillator, std::placeholders::_1, std::placeholders::_2);
std::function<double(Voice &, double)>callback2 = std::bind(&Oscillator::ModulatePitch, pOscillator, std::placeholders::_1, std::placeholders::_2);
std::cout << typeid(callback1).name();
std::cout << typeid(callback2).name();

你会发现返回的类型是不同的。在这种情况下，第二个bind尝试使用第二个类型构建它的对象(这不起作用)。我认为转换运算符(从bind到std::function)没有被外部bind调用存在问题。