Member Variable Pointer

Question

For a given struct:

struct foo
{
    void fooFunc(){}
    int fooVar = 0;
};

I can create a call wapper to the function: std::mem_fn( &foo::fooFunc ) such that I can pass it into another method and call it on an object.
I want to know if there is a similar call wrapper but for member variables.

For example I'm using a pointer to a member variable here and but I'd like to use an call wrapper:

void bar( std::function< void( foo ) > funcPtr, int foo::* varPtr )
{
    foo myFoo;
    funcPtr( myFoo );
    foo.*varPtr = 13;
}

Answer 1

N.B. Nothing in your question is from the STL (which is a library from the 1990s), std::function and std::mem_fn are part of the C++ Standard Library, which is not the same thing.

std::mem_fn supports member functions and member variables, so you can just do this to access the member variable and set it:

foo f;
std::function<int&(foo&)> var( std::mem_fn( &foo::fooVar ) );
var(f) = 1;