Question

I have a function:

std::function<void(sp_session*)> test(void(MainWindow::*handler)())
{
    return ...;
}

I would like to replace handler’s type with the equivalent std::mem_fn type.

What is the type?

I tried this:

std::function<void(sp_session*)> test(std::mem_fn<void(), MainWindow>  handler)    
{
    return ...;
}

But VC++ 2010 spits out these errors:

error C2146: syntax error : missing ')' before identifier 'handler'
error C2059: syntax error : ')'
error C2143: syntax error : missing ';' before '{'
error C2447: '{' : missing function header (old-style formal list?)

So I am not sure what I did wrong.

Answer 1

std::mem_fn is not the type you are looking for.
The type you need is std::function that takes the instance as argument:

std::function<void(sp_session*)> test(std::function<void(MainWindow *)> handler)

It can bind to member function and is just used with the instance as first parameter.
If in the original function you would do:

instance->*handler();

In the new function you do:

handler(instance);