template argument deduction/substitution failed, when using std::function and std::bind

Question

I have a compile error when using std::function in a templated member function, the following code is a simple example:

#include 
#include          


        

Answer 1

You can make type deduction work with some variant of:

template<typename CALLBACK>
void setCallback(CALLBACK cb) {
  typedef CALLBACK::first_argument_type T;
  static_assert(is_same_type<CALLBACK,function<void(T,int)>>::value);
  ...
}

This way CALLBACK can be determined by looking at the argument. It might get into trouble if bind doesn't actually return a std::function but rather something that can be cast as one. I'm not sure.

Answer 2

To figure out the problem let separate statements:

auto f = bind(&TestA::testa, &testA, _1, _2); // OK
test.setCallback(f);                          // <<--- Error is here

setCallback needs to know type of T and it can't deduce it from f, so give it a type

test.setCallback<TYPE>(f); // TYPE: int, float, a class, ...