AS3.0: Acces properties of created instance from 2nd class

I'm building a small game.

On my document class i create a instances of the class Character and Level with the following code:

//add the Level
level = new TileGrid();
level.y = 100;
level.x = 400;
addChild(player);

//add our player
player = new Character();
player.y = 150;
player.x = 400;
addChild(player);

I also create a controller class which handles the user input. (for example checks if the player is able to move to the right.)

I also create eventlisteners for keyboardevents and stuff.

When a key is pressed i want to check if the movement is possible by calling the checkTile(tileNumber) function of the 开发者_如何学编程TileGrid class from within the controller class.

The controller class looks like this:

package  {
    import flash.events.KeyboardEvent;
    import flash.events.Event;

    public class Controller{

    //Constructor code
    public function Controller(){}

    //Keyboard pressed -> move character
    public function keyPressed(evt:KeyboardEvent):void
    {
        trace(level.checkTile(30));
    }
}

And the TileGrid class looks something like this:

package  {
    import flash.events.KeyboardEvent;
    import flash.events.Event;

    public class TileGrid{

    //Constructor code
    public function TileGrid(){
        //Creating all the tiles and adding them to the stage.
    }

    //Check if a certain tile is walkable
    public function checkTile(tileNumberType){
        if(tileNumberType > 15){
            return false;
        }else{
           return true;
        }
    }
}

But when i test this i get the following error: Line 81 1120: Access of undefined property level.

When i try: trace(Object(parent).level.checkTile(30)); i get: 1120: Access of undefined property parent.

How can i access methods from one class with an instance from a second class ?

I think you must do something like this:

...
// somewhere in your document class (or somewhere else)
var player:Character = new Character();
var level:TileGrid = new TileGrid();
var controller:Controller = new Controller(player, level);
...

// in your Controller class

private var level:TileGrid;
private var player:Character;

public Controller(player:Character, level:TileGrid) {
    this.player = player;
    this.level = level;
}

public function keyPressed(event:KeyboardEvent):void {
    level.checkTile(30); // in this line "level" means "this.level"
}

In that case you must say which player and which level the controller must control. The controller is a class that has no knowledge of any other class. The variables are not global (in your example, and they shouldn't be) so you can't acces them from everywhere.

Classes in AS can't access their context. This means that if I have:

function foo():void
{
    var k:MyCustomClass = new MyCustomClass();
    var j:MyOtherClass  = new MyOtherClass();
}

the two instances j and k don't know about each other.

In this particular case, however, because you're clearly dealing with a parent structure, it is possible to get the parent's properties. This is possible because you have a path to the variable in a public scope.

Try this instead:

trace(Object(parent).level.checkTile(30));

Also note the Object(parent). A DisplayObject's parent is a DisplayObjectContainer, which does not have a level property. By wrapping parent in Object, however, you're telling Flash, "It's OK, you should look for this property at runtime not when compiling."