How to remove function pointer from std::deque by val?

Question

I am using std::deque to keep callback functions.

Everything works perfectly except removing a specific callback.

typedef std::function<void(void)> cb_Action;
std::deque<cb_Action> actionCallbacks;

I can Add items one by one or clear all of them without any problems.

But I cannot remove a specific callback from the deque variable.

actionCallbacks.erase ( std::remove(actionCallbacks.begin(), actionCallbacks.end(), callbackToRemove), actionCallbacks.end());

It gives compile time error:

binary '==': no operator found which takes a left-hand operand of type:'std::function<void(void)>' (or there is no acceptable conversion)

So, how can I remove a specific cb_Action ?

Answer 1

If you deal with usual functions you can do something like this based on std::function::target :

void callback_1(void) {}
void callback_2(void) {}

actionCallbacks = {
    std::function<void(void)>(callback_1),
    std::function<void(void)>(callback_2),
    std::function<void(void)>(callback_1)
};

actionCallbacks.erase(
    std::remove_if(actionCallbacks.begin(), actionCallbacks.end(), [](cb_Action action) {
        return (*action.target<void(*)(void)>() == callback_1);
    }),
    actionCallbacks.end()
);

Here all items with callback_1 inside are removed.