A
plugin is just a normal Impact module that lives in the
lib/plugins/ folder. This module may define one or more new classes or modify existing ones.
The whole idea of plugins is to have easily shareable code snippets that may be useful for a number of games. The
lib/plugins/ directory is just a convention - you don't have to use it, but if everybody uses it, it makes sharing these code snippets easier :)
Now, the difference between using
.inject() and
.extend() is, that
.inject() modifies an existing class
in place, whereas
.extend() creates a new one. Remember, plugins can do both: Some plugins, may offer completely new functionality, like a Camera class; some plugins may modify Impact's own classes.
Have a look at the tiny
map-size plugin. This plugin modifies
ig.Map using
.inject().
ig.Map is the super class (or
parent) of
ig.BackgroundMap and
ig.CollisionMap. Both of these super classes will have the properties and functions that were defined in the plugin.
Regarding your
Cannot call method 'bind' of undefined error:
ig.input is created when you call
ig.main() - so my guess is, you tried to create one of your button entities
before you called
ig.main().
To fix this, just create your buttons in the
init() method of your Game class (
lib/game/main.js). This method is the last step in initializing Impact. When your Game's
init() is called, everything else - ig.system, ig.input, ig.music and all assets - is ready.
If you really need a
postInit method for your entities, that is called when ALL entities have been added to the level, just... do it :)
// Add the postInit method to your entity class
EntityPlayer = ig.Entity.extend({
...
postInit: function() {
// do something!
}
});
// In your game class, call the postInit method on all entities after
// level loading is complete:
MyGame = ig.Game.extend({
...
loadLevel: function( data ) {
this.parent( data );
for( var i = 0; i < this.entities.length; i++ ) {
// Make sure this entity really has a postInit method
// before calling it
if( typeof(this.entities[i].postInit) == 'function' ) {
this.entities[i].postInit();
}
}
}
});
-
Update: I just noticed the first line from your Button snippet:
// sample use: play: new EntityButton('media/play.png', 200, 200, this, 'play');
So I guess you were using it like so:
MyGame = ig.Game.extend({
// This wont work as expected!
buttonPlay: new EntityButton('media/play.png', 200, 200, this, 'play');
...
});
This will create the Entity instance as soon as the Game class (
not the instance of that class) is created. At this time, neither ig.system, ig.input, ig.game or anything else is ready. The browser is still busy
loading the modules and Impact hasn't even begun to load the graphics and sounds, let alone started the game.
Also, just creating an Entity like this wont add it to the game world. Impact doesn't know it's there; it won't call the
.update() or
.draw() method of this entity. Use
.spawnEntity if you want to add entities to the game world
by hand (i.e. not load them with the level).
But I don't think you want your buttons to be Entities at all. When you load a new level, all buttons will be removed. After all, Entities are objects
in the game world.
Instead, just subclass your Buttons from
ig.Class, give them a
.update() and
.draw() method and call these methods for each of your buttons in your Game's
.update() and
.draw(). You may want to add an array to your Game that holds all these buttons.
