How to Correctly Bind C Member Functions to std::function Objects?

Binding Member Functions to Generic std::function Objects

In C , you may encounter situations where you need to store function pointers to member functions of a particular class in a container that accepts std::function objects. However, attempting to bind a non-static member function directly to a std::function can lead to errors.

Consider the following code:

#include <functional>

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

This code will result in a compiler error because non-static member functions implicitly accept a "this" pointer as their first argument. To resolve this issue, you need to bind the object in advance using the std::bind function.

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

This version correctly binds the "this" pointer to the member function, allowing you to store it in the std::function object without triggering the error.

For member functions that accept parameters, you can use std::placeholders to specify their positions:

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

Alternatively, if your compiler supports C 11 lambdas, you can use them to create the std::function object:

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

By utilizing these techniques, you can effectively bind member functions to generic std::function objects, enabling you to store and manipulate them conveniently.

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