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injector.mapSingleton(Model); but [inject] public var board:Model; returns a null.

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davidtynnhammar

09 Aug, 2010 06:16 PM

Hello.

In my main context I have a injector.mapSingleton(Model);. Then when I try to access the model in a command by doing [inject] public var model:Model; all I get when I try to access this model is a null.

The model is extending from Actor and the command obviously extends Command.

I get no error messages except for the exception when trying to access that null objects methods.

What have I missed?

1. Support Staff 1 Posted by Joel Hooks on 09 Aug, 2010 06:34 PM

   

   It is hard to tell what you missed without more context ;)

   Can you paste in the actual code (the command and context) and specify where in the command it is null.

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2. Support Staff 2 Posted by Shaun Smith on 09 Aug, 2010 06:40 PM

   

   Perhaps it is null in your command's constructor? Dependencies injected via setter/property injection are not available until after the instance has been created. Have a look at: http://wiki.github.com/robotlegs/robotlegs-framework/common-problems (under "Problem: Injected Properties Are Null In Constructor").

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3. 3 Posted by davidtynnhammar on 09 Aug, 2010 06:55 PM

   

   ` public class MyContext extends Context {
   

   public function MyContext(contextView:DisplayObjectContainer) {     
       super(contextView);
   }
   
   override public function startup():void {
   
           injector.mapSingleton(Model);
   
       commandMap.mapEvent(MEvent.TRY_MOVE, ACommand, MEvent);
   
       super.startup();
   }

   }`

   ` public class ACommand extends Command {
   

   [inject]
   public var m:Model;
   
   public function ACommand(e:MEvent) {
       trace(m);
   
   }

   } `

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4. 4 Posted by davidtynnhammar on 09 Aug, 2010 06:57 PM

   

   Err.. Seems like I can't make it format correctly, but I hope you can understand it anyway :). (Thanks for the quick replies!)

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5. Support Staff 5 Posted by Joel Hooks on 09 Aug, 2010 07:00 PM

   

   The property injection isn't available yet. It will be available for the execute() method of the command. To get the injection in the constructor you could:

   public function ACommand(e:MEvent, m:Model) {
   

    this.m = m;
    trace(m);

   }

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6. 6 Posted by Jason Dias on 09 Aug, 2010 07:01 PM

   

   Your command should overwrite execute, if for some reason you need the model
   available in the constructor of the command you need to use [PostContruct]
   tag as Shaun described here
   http://wiki.github.com/robotlegs/robotlegs-framework/common-problems (under
   "Problem: Injected Properties Are Null In Constructor").

   On Mon, Aug 9, 2010 at 11:57 AM, davidtynnhammar <
   [email blocked]<tender%[email blocked]>
   > wrote:

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7. Support Staff 7 Posted by Joel Hooks on 09 Aug, 2010 07:08 PM

   

   There are one or two use cases for PostCostruct, and this likely isn't one of them - it also wouldn't change the unavailability of the property value in the constructor. Using constructor injection is a cleaner solution, so I guess I disagree with Shaun on this one.

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8. 8 Posted by Jason Dias on 09 Aug, 2010 07:15 PM

   

   I also agree, in my opinion PostConstruct in a command means the command is doing to much.

   Here is an example of one of my commands,

   package {

   import UserCarRideHeightEvent;
   
   import UserModelManager;
   import UserCar;
   
   import org.robotlegs.mvcs.Command;
   
   public class UpdateUserCarRideHeight extends Command
   {
       [Inject]
       public var event:UserCarRideHeightEvent;
   
       [Inject]
       public var userModelManager:UserModelManager;
   
       override public function execute():void
       {
           var myUserCar:UserCar =  userModelManager.getUserCarByUserCarID(event.userCarID);
           myUserCar.rideHeight = event.rideHeight;
       }
   }

   }

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9. 9 Posted by davidtynnhammar on 10 Aug, 2010 04:56 AM

   

   ´public class TryMoveCommand extends Command {
   

   [inject]
   public var m:dModel;
   
   override public function execute():void {
           trace(m);
   }

   }´

   This still prints out null's.

   Edit: And I'm not using the constructor anymore.

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10. Support Staff 10 Posted by Ondina D.F. on 10 Aug, 2010 06:12 AM

    

    Hi David,

    maybe the [inject] is just a typo in your post, but if you have it like this in your code as well, that could be the cause for the error in your command.
    [Inject] has to be written with a capital I.

    Ondina

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11. 11 Posted by Nikos on 10 Aug, 2010 10:13 AM

    

    @Jason

    Nice code

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12. 12 Posted by davidtynnhammar on 11 Aug, 2010 06:22 AM

    

    It was a typo (in my original code that is). How embarrasing.

    Thanks guys!

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13. davidtynnhammar closed this discussion on 11 Aug, 2010 06:22 AM.