Passing member function as a callback to a template function

Question

I'm trying to pass a member function as an argument to a template function. I have read all the threads in Stackoverflow about passing member functions as arguments to other functions. But, somehow I don't get this simple thing to work:

template <typename T>
T Class::registerCallback(std::function<T()> callback) {
  // do something
}
bool Class::member() {
  return true;
}
void Class::method() {
  registerCallback(std::bind(&Class::member, this, std::placeholders::_1));
}

The error message I receive is:

no matching member function for call to 'registerCallback'

I have tried to solve this for a long time. I would be very grateful if someone can point me out what is wrong.

Answer 1

The callback that must be registered does not have any parameters.

std::function< T() >

However, you try to register a callback which accepts a single parameter.

std::bind(&Class::member, this, std::placeholders::_1)

Furthermore, the Class::member function doesn't have any parameters.

Try this:

class Class
{
public:
    // I'm not sure why this was returning a 'T' changed to 'void'
    template<typename T>
    void registerCallback(std::function<T()> callback)
    {
        // do something
    }

    void method()
    {
        // The 'member' function doesn't have any parameters so '_1' was removed
        registerCallback<bool>(std::bind(&Class::member, this));
    }

    // The callback is supposed to return 'T' so I changed this from 'bool'
    bool member()
    {
        return true;
    }
};

int main()
{
    Class<bool> c;
    c.method();

    return 0;
}