Action class in C++? (equivalent to C#)

action, c#, c++, delegates, lambda

Solution

You can use `std::function` in place of `Action`:

typedef std::function<void()> Action;
std::vector<std::pair<Action, int> > DrawActions;
void Draw() {
    for_each(DrawActions.begin(), DrawActions.end(), [](std::pair<Action, int>& a) {
       a.first(); 
    });
}

Problem

In my C# game engine, I used to handle ordered drawing by adding/removing action to a manager object, which sorted the actions by priority, then executed them. Here is a very simplified example: ``` class DrawManager { public List<Tuple<Action, int>> DrawActions = new List<Tuple<Action, int>>(); void Draw() { foreach (var tuple in DrawActions) tuple.Item1(); } } class Example { DrawManager manager; Example() { manager.DrawActions.Add(new Tuple<Action, int>(DrawBackground, 0)); manager.DrawActions.Add(new Tuple<Action, int>(DrawForeground, 100)); } ~Example() { manager.DrawActions.Remove(manager.DrawActions.Find(x => x.Item1 == DrawBackground)); manager.DrawActions.Remove(manager.DrawActions.Find(x => x.Item1 == DrawForeground)); } void DrawBackground() { /* draw something */ } void DrawForeground() { /* draw something */ } } ``` By adding some helper methods, the code becomes very elegant and easy to use in my engine. I've moved to C++ recently, and I can't find any easy way to achieve the same result. I tried using std::function, but in order to remove the method on object destruction, I had to store the draw method in a pointer owned by the caller, then wrap it into a lambda and pass it in. Very inelegant and time consuming. Is there any way to get code similar to the one shown in the C# example?

Original source