Access of undefined property issues in AS3 - actionscript-3

Question

I am having a bit of trouble with some AS3. First time using this language and have more experience with web development then OOP so am getting a bit confused.
I am trying to make it so that when someone clicks a 'powerbutton' which is a "movieclip" symbol within flash then another symbol should then become visible. This is all being done within the Kitchen class.
The code for the main class is which i got from a youtube tutorial video i followed;
package {
import flash.display.MovieClip;
import flash.events.MouseEvent;
import flash.geom.Point;
import flash.events.Event;
import Kitchen
public class DragFood extends MovieClip
{
protected var originalPosition:Point;
var myKitchen:Kitchen
public function DragFood() {
myKitchen = new Kitchen;
originalPosition = new Point (x, y);
buttonMode = true;
addEventListener (MouseEvent.MOUSE_DOWN, down);
}
protected function down (event:MouseEvent):void
{
parent.addChild(this);
startDrag();
stage.addEventListener (MouseEvent.MOUSE_UP, stageUp);
}
protected function stageUp (event:MouseEvent):void
{
stage.removeEventListener (MouseEvent.MOUSE_UP, stageUp);
stopDrag();
if (dropTarget)
{
if(dropTarget.parent.name == "bowl")
{
trace("The " + this.name + " is in the bowl");
this.visible = false;
} else {
returnToOriginalPosition();
}
} else {
returnToOriginalPosition();
}
}
protected function returnToOriginalPosition():void
{
x = originalPosition.x;
y = originalPosition.y;
}
}
}
Within it i call the other class;
import Kitchen
public class DragFood extends MovieClip
{
protected var originalPosition:Point;
var myKitchen:Kitchen
The code for the kitchen class is;
package {
import flash.display.MovieClip;
import flash.events.MouseEvent;
import flash.events.Event;
public class Kitchen extends MovieClip
{
// This is a function. This particular function has the same name as our class and therefore will be executed first
public function Kitchen()
{
// This is a "call" to another function that is defined later in the program.
init();
trace("Hello world");
}
public function init():void
{
// If we want an object (on the screen or otherwise) to be notified about an event we must add a listener for that event to that object.
// We also need to specify what happens everytime the event we are listening for happens.
PowerButton.addEventListener(MouseEvent.CLICK, handleButtonClicks);
}
//This function is called when the oven on button recieves a click.
public function handleButtonClicks(event:MouseEvent):void
{
OvenOn.visible = true;
trace("the oven is being switched on");
}
}
}
The issue i keep getting is that OvenOn and PowerButton are giving me a undefined access issue and im not sure how to fix it. I have found posts on similar subjects like - Access of Undefined property? Actionscript 3
but im not quite sure how to apply it to my issue if anyone could offer any help that would be great.

Answer 1

When you're programming on the timeline, code is referencing the local namespace, and objects you make there (movieclips, textfields, etc.) are automatically instantiated in that namespace so that you can simply call OvenOn.visible = true. However, for each class, their local namespace is whatever is inside the class, so unless you actually created a property on your class called OvenOn, it will most definitely give you Access of Undefined Property errors.
Think of each class as its own island. For them to touch eachother, they need some sort of connection. That connection can be made once the parent instantiates the class in its own namespace. For example...
var foo:String = "Hello!";
var bar:MyClass = new MyClass();
// At this point, whatever code runs inside of MyClass has no concept of foo, or how to access it.
addChild(bar);
// Now that we've added it to the stage, the bar has some properties that have automatically been populated such as "root", "parent", or "stage".
foo.someProperty = "World";
// Since this namespace has a variable pointing to the instance, we can change properties on that class.
Now that we've instantiated MyClass on the stage, we can reference parent properties the class didn't know about. Mind you, this is not necessarily best practice.
package
public class MyClass extends MovieClip {
var someProperty:String = "cheese";
public function MyClass() {
trace(parent.foo) // this will fail
addEventListener(Event.ADDED_TO_STAGE, test);
}
public function test(e:Event):void {
trace(this["parent"].foo); // this will succeed
}
}
}
If you absolutely must change something that is not part of your Kitchen class, pass either the parent of OvenOn or that object specifically as a property of Kitchen. You could do this a couple ways.
with the Constructor...
var something:*;
public function MyClass(someObject:*) {
something = someObject;
}
public function test():void {
something.visible = false;
}
...or by Assigning the Property...
var bar:MyClass = new MyClass();
bar.something = OvenOn;
bar.test(); // will turn off the OvenOn now that 'something' is pointing to it.