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injected model (singleton) equals null

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patryk

09 Jul, 2011 06:51 PM

In main context:

injector.mapSingletonOf( IWorldModel, WorldModel );

In some command:
(it works fine)

[Inject] public var worldModel :IWorldModel;

In another model:
( this doesn't work, worldModel == null )

[Inject] public var worldModel :IWorldModel;

What could I be doing wrong?

1. 1 Posted by Stray on 09 Jul, 2011 06:56 PM

   

   Hi patryk - on the front of the forum is a link to our 'common problems' documentation - that has a great section all about null injector errors - it's usually one of half a dozen simple things, so that's the place to start.

   In a nutshell:

   - typo in [Inject]
   - race conditions (the model needing the mapping is asking for it before the mapping has been made)
   - accidental ; after [Inject]

   hth,

   Stray

   • Edit

2. 2 Posted by patryk on 09 Jul, 2011 07:10 PM

   

   Thank you for a quick reply Stray.

   No typos, mapping is done before injection...
   I just checked the common problems doc, and I can not find anything wrong in the code.

   public class WorldModel extends Actor implements IWorldModel
   {
   private var robotVector :Vector.<IRobotModel> = new Vector.<IRobotModel>;
   .
   .
   .
   }.

   public function addRobot( robotModel:IRobotModel ):void
   {
   robotModel.grid = getGrid( robotModel.robotView );
   
   robotVector[ robotVector.length ] = robotModel;

   dispatch( new RobotEvent( RobotEvent.ROBOT_CREATED, robotModel ) );
   }

   ------ that RobotEvent is mapped to DisplayRobotCommand:

   public class DisplayRobotCommand extends Command
   {
   [Inject]
   public var worldModel :IWorldModel;
   
   override public function execute():void
   {
   worldModel.world.add( event.robotModel.robotView ); /// HERE THE INJECTION WORKS
   }
   }

   -------- and then in WorldModel:

   private function onTimer( e:TimerEvent ):void
   {
   for ( var i:int = 0; i < robotVector.length; i++ ) robotVector[ i ].oEF();
   }

   ---------- and inside that robotModel:

   public class PlayerRobotModel implements IRobotModel
   {
   [Inject]
   public var worldModel :IWorldModel;
   
   private var _robotView :RobotView;
   
   public function oEF():void
   {
   MonsterDebugger.trace( this, worldModel, "worldModel"); ////// AND HERE COMES THE ERROR:

   TypeError: Error #1009: Cannot access a property or method of a null object reference.

   
   What am I doing something wrong here?

   BTW, What tags can I use to format the code in this post?

   • Edit

3. 3 Posted by Stray on 09 Jul, 2011 09:02 PM

   

   Hi Patryk, the things in common problems, plus the race conditions, are the only things I've ever heard of being problems.

   But please do paste your code - I won't get a chance to look before tomorrow now (10pm here in uk) but hopefully someone else will :)

   Stray

   • Edit

4. 4 Posted by patryk on 09 Jul, 2011 09:09 PM

   

   Thanks a lot Stray.

   How can I get this trace of the order of mapping, etc ?
   I have seen it somewhere on this forum but can't find it.

   BTW: 10pm here too, in Southampton :)

   • Edit

5. Support Staff 5 Posted by Stray on 09 Jul, 2011 10:40 PM

   

   How is PlayerRobotModel being created? You're not doing new PlayerRobotModel() are you?

   Just a thought... the injector has to be used to create any instance requiring injections.

   • Edit

6. 6 Posted by patryk on 09 Jul, 2011 10:45 PM

   

   I am doing this in one of the commands:

   dispatch( new RobotEvent( RobotEvent.CREATE_ROBOT, new PlayerRobotModel( new RobotView( 4, 0xFF3399, 4, 30, 290, 20 ) ) ) );

   • Edit

7. 7 Posted by Stray on 09 Jul, 2011 10:49 PM

   

   Ah - ok, that's it then!

   Instead, do:

   var playerRobotModel: PlayerRobotModel = new PlayerRobotModel( new RobotView( 4, 0xFF3399, 4, 30, 290, 20 ) );
   injector.injectInto(playerRobotModel);

   dispatch( new RobotEvent( RobotEvent.CREATE_ROBOT, playerRobotModel) );

   Injection isn't *magic* - it's just a smart factory - you still have to use the injector to fulfil the injections :)

   Stray

   • Edit

8. 8 Posted by patryk on 09 Jul, 2011 11:24 PM

   

   Yes, that was it :)

   Thank you very much for your help Stray, much appreciated.

   • Edit

9. Ondina D.F. closed this discussion on 01 Nov, 2011 04:13 PM.