Question

I’m building a mobile AIR app using Flash Builder 4.5. The initial view in my views package is TestHomeView.mxml. I want to refer to it in one of my .as classes elsewhere in the app, and I’m not sure how to do that.

Theoretically I should be able to add an “id” attribute to TestHomeView.mxml, but FB gives me an error: “id is not allowed on the root tag of a component”. The root tag is s:view.

The reason I need to do this is that within another class I make various calculations and then need to pass an array of values to a component in my view class. So in SomeOtherActionScriptClass.as I first assemble the array, myArray, and then in that class I want to do this:

 myViewComponent.viewArray = myArray;

If I’m going to do that, I also need to import the view class into the .as class, which strikes me as weird. So is there a simple way to do what I want, or do I have to dispatch a custom event which contains the array, and listen for it in the view class?

EDIT – Based on the below MVC suggestion I did the following in model:

    [Bindable]
public class Model
    {
    private static var myModel:Model;//doesn't let me name it 'model' because
                                     //I have a package named 'model'
    public var myArray:Array;  //its value set later in model code
public function Model()
{
    if ( Model.myModel != null ){
        throw new Error( "Only one Model instance should be instantiated" );
        }
    }

    // singleton: always returns the one existing static instance to itself
    public static function getInstance() : Model {
        if ( myModel == null ){
            myModel = new Model();
        }
        return myModel;
    }

Then in the view code I have:

[Bindable] //do I actually need this?
private var myModel:Model = Model.getInstance();
var viewArray = new Array();
viewArray = myModel.myArray;

But it is coming back null. It isn’t null when I put a breakpoint in the Model class, but when I try to access it from the view class, it’s null. The model itself isn’t null, but that variable is.

What am I doing wrong?

Thanks.

Answer 1

First, if you are trying to make a singleton in AS3 you should first create a class, within the same class file as Model, that is used to ensure you can only create the class once.

Add this class at the bottom of the Model class file (outside of the Model class):

internal class SingletonEnforcer{} 

Then create the Model constructor like this:

public function Model(enforcer:SingletonEnforcer){ Init(); } // if init code is needed

public static function get Instance():Model
{
    if (!myModel){
        myModel = new Model(new SingletonEnforcer());
    }
    return myModel;
}

Now you don’t have to throw an exception for creating a second instance because it isn’t possible.

I’m not sure about your first question of referencing your app’s main mxml, but if you were asking how to call the app that is running (like WindowedApplication in AIR) then you would call it like this:

// my WindowedApplication file = MyApp.mxml
MyApp(this.parentApplication)

That will return the app’s instance.

Once you’ve set up the Singleton like I have it above you should be able to access your array like:

Model.Instance.myArray;

I hope this helps!