title: SKLabelNode text values won't update when stored in an NSMutableArray
body: <p>If I change the <code>text</code> attribute on a <code>SKLabelNode</code> after adding it as a child, the text will update in the view. But if I add it to an <code>NSMutableArray</code>, retrieve it, and <em>then</em> change the value, the text will not update in the view.</p>
  
  <p>My best guess would be that either <code>-addObject:</code> or <code>-objectAtIndex:</code> of <code>NSMutableArray</code> are copying the objects instead of referencing them, but as you can see from their documentation: (<a href="https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSMutableArray_Class/Reference/Reference.html#//apple_ref/occ/instm/NSMutableArray/addObject%3a" rel="nofollow"><code>-addObject:</code></a>, <a href="https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSArray_Class/NSArray.html#//apple_ref/occ/instm/NSArray/objectAtIndex%3a" rel="nofollow"><code>-objectAtIndex:</code></a>), neither one says anything about objects being copied.</p>
  
  <p><em>Note: you may need to reload the pages for the <code>-addObject:</code> and <code>-objectAtIndex:</code> documentation before you're taken to the right spot on the page.</em></p>
  
  <p>What's going on? Why aren't my changes propagating?</p>
  
  <p><code>MyScene.h</code>:</p>
  
  <pre><code>#import &lt;SpriteKit/SpriteKit.h&gt;
  
  @interface MyScene : SKScene
  
  @property(nonatomic, strong) NSMutableArray *labels;
  
  @end
  </code></pre>
  
  <p><code>MyScene.m</code>:</p>
  
  <pre><code>#import "MyScene.h"
  
  @implementation MyScene
  
  @synthesize labels;
  
  -(id)initWithSize:(CGSize)size {
      if (self = [super initWithSize:size]) {
  
          self.backgroundColor = [SKColor colorWithRed:0.15 green:0.15 blue:0.3 alpha:1.0];
  
          SKLabelNode *label = [SKLabelNode labelNodeWithFontNamed:@"Consolas"];
  
          label.text = @"Test String";
          label.fontSize = 65;
          label.position = CGPointMake(CGRectGetMidX(self.frame),
                                       CGRectGetMidY(self.frame));
          [labels addObject:label];
          [self addChild:label];
  
          // If I uncomment the following line, the text won't update.
          // label = [labels objectAtIndex:0];
  
          label.text = @"Test String: Reloaded";
      }
      return self;
  }
  
  @end
  </code></pre>