Game Development Reference
In-Depth Information
var p = Ship.prototype = new createjs.Sprite();
p.Sprite_initialize = p.initialize;
p.initialize = function (spritesheet) {
this.Sprite_initialize(spritesheet);
}
window.sprites.Ship = Ship;
}());
The sprite sheet object is passed into the instance of the sprite and is passed along to the
initialize
function
so it can be used when calling the super's initializing function. Note that your namespacing code is not necessary to
extend
Sprite
, but you will be using it here as you did with the UI elements to keep them out of the global space.
window.sprites = window.sprites || {};
Using Custom Sprites
As you would expect, using custom sprites in your application is as easy as using one out of the box. Your custom
sprite will need a sprite sheet, so be sure you have one ready before trying to add your new sprites to the stage.
The following is an example of a custom sprite being instantiated by passing it an existing sprite sheet:
var ship = new sprites.Ship(shipSpriteSheet);
addChild(ship);
Your custom sprites will often contain methods to act or animate in certain ways, depending on the situation in
your game. Listing 8-15 shows a custom property and some methods that might be added to a
Ship
class.
Listing 8-15.
Example of Extending Sprite for a Ship Class
p.points = 10;
p.die = function(){
this.gotoAndPlay('explode');
this.on('animationend',this.destroy);
}
p.destroy = function(){
this.parent.removeChild(this);
this = null;
}
You can then use this ship in the following way:
score += ship.points;
ship.die();
This will increment a
score
variable by the value of the
points
property on the
ship
instance. The ship will
clean itself up by playing an
explode
sequence, then removing itself from the container it's in when the animation
has ended.
