Actor and Sprite, who should own these properties?
- by Gerardo Marset
I'm writing sort of a 2D game engine for making the process of creating games easier. It has two classes, Actor and Sprite. Actor is used for interactive elements (the player, enemies, bullets, a menu, an invisible instance that controls score, etc) and Sprite is used for animated (or not) images with transparency (or not).
The actor may have an assigned sprite that represents it on the screen, which may change during the game. E.g. in a top-down action game you may have an actor with a sprite of a little guy that changes when attacking, walking, and facing different directions, etc.
Currently the actor has x and y properties (its coordinates in the screen), while the sprite has an index property (the number of the frame currently being shown by the sprite).
Since the sprite doesn't know which actor it belongs to (or if it belongs to an actor at all), the actor must pass its x and y coordinates when drawing the sprite.
Also, since a actors may reset its sprite each frame (and usually do), the sprite's index property must be passed from the old to the new sprite like so (pseudocode):
function change_sprite(new_sprite)
old_index = my.sprite.index
my.sprite = new_sprite()
my.sprite.index = old_index % my.sprite.frames
end
I always thought this was kind of cumbersome, but it never was a big problem.
Now I decided to add support for more properties. Namely a property to draw the sprite rotated, a property to draw it flipped, it a property draw it stretched, etc. These should probably belong to the sprite and not the actor, but if they do, the actor would have to pass them from the old to the new sprite each time it changes... On the other hand, if they belonged to the actor, the actor would have to pass each property to the sprite when drawing it (since the sprite doesn't know which actor it belongs to, and it shouldn't, since sprites aren't just meant to be used by actors, really). Another option I thought of would be having an extra class that owns all these properties (plus index, x and y) and links an actor with a sprite, but that doesn't come without drawbacks.
So, what should I do with all these properties?
Thanks!
