CODEWITHSUNDEEP
c#eventsdictionarymonogame
Giora Guttsait
Giora Guttsait

Reputation: 1300

Dictionary of events (each value can hold several methods)

I've tried looking for an answer here in previous posts, but I didn't find one.
I'm doing a MonoGame game, and I decided I want to have a event based keyboard handler.

So the KeyboardHandler class is a singleton class, And right now it has:
- delegate void KeyPressEventHandler()
- events of that delegate for the four arrow keys
- static instance of the class for singleton
- get method for that instance
- A while(true) thread method and a method that creates a thread that calls that method.

The thread method is just a while(true) that checks if a keypress of any of the the four arrow keys have been pressed and activates their respective event if needed.

I want to be able to create a dictionary of <Keys, (event or whatever)> so that I can for example:

void doSomething() { }
KeyboardHandler.Get().SubscribeToEvent(Keys.A, doSomething)
void SubscribeToEvent(Keys key, Action toSubscribe)
{
    this.KeypressHandler[key] += new KeypressEventHandler(tobSubscribe)
}

And a method that would handle firing these event handlers of course.

But How do I declare such a dictionary?

EDIT: eventually implemented here: https://github.com/gioragutt/training/blob/master/MonoGameFirst/MonoGameFirst/BaseGameClasses/KeyboardHandler.cs

Upvotes: 2

Views: 949

Answers (1)

ryanyuyu
ryanyuyu

Reputation: 6486

Just declare you dictionary as a Dictionary<Keys, Action>. Then you just have to check whether your dictionary actually contains that key. Remember that the standard Action is just a method that has 0 input arguments and does not return a value. If you need, you could use one of the other Actions that accept a set number of input arguments. Your code might resemble something like this:

Setup your dictionary:

var keyHandlers = new Dictionary<Keys, Action>(); 
keyHandlers.Add(Keys.Back, () => Console.WriteLine("Handler for backspace"));
keyHandlers.Add(Keys.Enter, () => {
    //some other statements, 
    //maybe set some class-level property 
    Console.WriteLine("Handler for enter ");
});
keyHandlers.Add(3, NameOfMethodThatMatchesActionDelegateSignature);

Then in the main event handler, check the dictionary and try to do stuff:

Action actionToDo;
bool actionRegistered = keyHandlers.TryGetValue(key, out actionToDo);
if (actionRegistered)
{
    actionToDo.Invoke();
}

A demo that uses ints to register the actions instead of the Keys enum.

Upvotes: 1

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