Passing data between views and models in Flex MVC framework - apache-flex

Question

I have never used Flex/Actionscript before so excuse me if I'm asking anything obvious but I have been working on this for 3 days (includes searching google and stackoverflow) before writing this post.
I have been asked to modify a game written in Flex 4 made with a mini-IoC-based MVC framework. Two mods I have been asked to make is a game over screen, which displays the final score and a difficulty selection on the introduction screen. I have made the game over screen, and successfully managed to get the controller to bring it up when the game timer runs out.
So for now, the game structure goes:
Intro View -> Game View -> Game Over View
^ |
|__________ (retry?) ________|
The first problem is getting the score to be passed from the mainGame ActionScript file to the game over screen.
Things I have tried:
Importing mainGame in the gameOverViewBase and calling the mainGame.score variable in the gameOverView mxml file.
-EDIT!!! = the above method works if I change the score variable in mainGame to a constant, but if it remains a variable, the controller won't load the gameOverView and the game sits at an empty mainGame view.
Making a function that adds to a new score variable in the gameOverViewBase whenever the player scores during the game.
Passing the score as a parameter to the GameOverView when the MainGame ends
controller.loadGameOver(score);
This seemed like the most logical way to go about it. So I followed the function through the other components of the game setting the loadGameOver to take an integer as a parameter until I got to the main game actionscript file:
public function loadGameOver(score:int) : void
{
loadView(GameOverView);
}
The loadView function (shown below) is where I get stuck because I can't see where to pass the 'score' parameter. It looks like this:
private function loadView(viewClass:Class, modelClass:Class = null) : void
{
var view:View = new viewClass();
if(!view) throw new Error("Could not load view");
viewContainer.removeAllElements();
viewContainer.addElement(view);
view.controller = this;
}
The second problem is the difficulty selection on the introduction screen. I have done this with 3 buttons (easy, normal, hard) in the mxml file and for every button in the ActionScript:
protected function onEasyButtonClick() : void
{
set = "easy"
controller.loadMainGame(set);
}
Once again, I end up at the above loadView function.
To sum up: I need to know how to pass the data between the views and models. If that's not the ideal method, I am open to any other methods that you think are better.
Thank You!
Ben
P.S. I can send my source code to anyone who would like to help :)

Answer 1

You don't specify which MVC framework you're using which would be helpful. However, score should definitely be a property of a model and the model data should be accessible to the view either directly, perhaps via binding (thanks weltraumpirat), or via some intermediary class.
I would suggest you have a look at some of the existing view classes and try to figure out how they are fed the model data. You can use this approach to get the data you need for your view.
[EDIT]:
The mainGame property is not being set on your GameOverView instance so you're unable to access its score property either through binding or through trace. The loadView method of your controller class accepts a Model class reference which it uses to construct a new Model instance to be used by the new View. Unfortunately this is no use to you as your GameOverView needs the instance of MainGame which was created for the MainGameView (and which contains the current score).
I don't know if the following fits into the philosophy of the framework you're using. However, I would change the loadView method to accept an instance of a Model rather than a class reference, and create and cache a reference to an instance of MainGame when your controller is instantiated. That way you can pass the same Model reference to both the MainGameView and GameOverView when these are created.
public class WhackAMoleBase extends Application implements IGameController
{
public var viewContainer:Group;
private var mainGame:MainGame
public function WhackAMoleBase() : void
{
super();
// Create and cache an instance of the main game Model
mainGame = new MainGame();
addEventListener(FlexEvent.CREATION_COMPLETE, onCreationComplete);
}
public function loadIntroduction() : void
{
loadView(IntroductionView);
}
public function loadMainGame() : void
{
loadView(MainGameView, mainGame);
}
public function loadGameOver() : void
{
// Use the same instance of MainGame which the MainGameView
// has been using as the Model for the GameOverView
loadView(GameOverView, mainGame);
}
// Accept a Model instance rather than a class Reference
private function loadView(viewClass:Class, model:Model = null) : void
{
//Create a new instance of the supplied view
var view:View = new viewClass();
if(!view) throw new Error("Could not load view");
//Clear any previous views in the container and add
viewContainer.removeAllElements();
viewContainer.addElement(view);
//Property based dependency injection
view.controller = this;
//There may or may not be a model required for the
//requested view; check and instantiate appropriately
if(model)
{
//Give model reference to the controller
//and link the view up to the model
model.controller = this;
view.model = model;
}
}
private function onCreationComplete(event:FlexEvent) : void
{
//When the application is first created, we want to show the introductory view
loadView(IntroductionView);
}
}