How to Correctly Use Member Function Pointers with std::function?

How to Handle Member Function Pointers in std::function Objects

When working with member functions within std::function objects, certain complications can arise. Consider the following code:

#include <functional>

class Foo {
public:
    void doSomething() {}
    void bindFunction() {
        // ERROR
        std::function<void(void)> f = &Foo::doSomething;
    }
};

An error arises because non-static member functions implicitly pass the "this" pointer as an argument. However, the std::function signature here does not account for this argument.

Solution: Binding Member Functions to std::function Objects

To address this issue, the first argument ("this") must be explicitly bound:

std::function<void(void)> f = std::bind(&Foo::doSomething, this);

For functions with parameters, placeholders can be utilized:

using namespace std::placeholders;
std::function<void(int, int)> f = std::bind(&Foo::doSomethingArgs, this, _1, _2);

In C 11, lambdas can also be employed:

std::function<void(int, int)> f = [=](int a, int b) {
    this->doSomethingArgs(a, b);
};

By incorporating these techniques, programmers can successfully work with member function pointers within std::function objects, effectively managing the implicit "this" argument.

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