Question

Essentially I’m trying to find out whether I should be storing a reference to the service I retrieve or if I can simply call GetService every time I need it.

A perfect example of what I’m using this with is SpriteBatch. Instead of having an object store a reference to the SpriteBatch, I call

    SpriteBatch spriteBatch = (SpriteBatch)Game.Services.GetService(typeof(SpriteBatch)); 

at the beginning of every Draw() method that needs it.

In conclusion, what is the Big O of GetService()? This will help me decide. I’m assuming it’s a hash table so generally O(1)?

Answer 1

The Big-O of GetService is irrelevant, because you have a small and constant number of services in there. So effectively calling GetService is a constant-time O(1) operation. (Internally it uses a Dictionary – I couldn’t easily track down a definitive answer on its Big-O, but I imagine it’s pretty good).

Is it a lot slower than getting a reference? Yes.

Is it too slow for a game world with, say, 100 gameplay objects? No.

Is it too slow for each of 100000 particles in a particle system? Yes.

Is using a services architecture for this a bad idea, even if you ignore performance and consider only an architectural point of view? Yes.