如何将 void 转换为 typedef void(...)(float)

Question

I have this on one class:

typedef void(*PERCENTAGE_CALLBACK)(float);

And I use it on functions like this one:

int API_GenerateLayerData(int layerIndex, QByteArray data, int dataSize, PERCENTAGE_CALLBACK callBack);

But the thing is that I can't pass a parameter with a void return type and accepts float as a parameter like this:

void updateFormattingProcess(float value)
{
    emit ChangeCompose(int(value));
}

void someFunction()
{ 
    //It says cannot convert from 'void' to 'PERCENTAGE_CALLBACK'
    API_GenerateLayerData(1, data, count, updateFormattingProcess(x));
}

Answer 1

You are trying to call the function with updateFormattingProcess(x) and pass the result of that function call (which is void ) as a parameter of type void(*)(float) . Instead, just pass a pointer to it:

API_GenerateLayerData(1, data, count, &updateFormattingProcess);
//                                    ^ take the addresss of the function