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

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(f); // TYPE: int, float, a class, ...