title: Can I declare a NSMutableArray as a property in a Shared Object
body: <p>I/m developing for iOS 7 and using arc. I'm trying to create a shred instance that contains an NSMutableArray and having some trouble. 
  in my header file I have the following</p>
  
  <pre><code>#import &lt;Foundation/Foundation.h&gt;
  
  @interface SharedDataController : NSObject
  
  @property (nonatomic, retain) NSString *text1;
  @property (nonatomic, retain) NSString *text2;
  @property (nonatomic, retain) NSString *text3;
  @property (nonatomic, retain) NSMutableArray *qrcodes;
  
  +(id) sharedInstance;
  
  @end
  </code></pre>
  
  <p>and in my implimentation</p>
  
  <pre><code>@synthesize text1,text2,text3, qrcodes;
  
  +(id) sharedInstance
  {
      static id sharedInstance = nil;
      if (sharedInstance == nil) {
          NSLog(@"creating shared instance contoller");
          sharedInstance = [[self alloc] init];
      }
      return sharedInstance;
  }
  
  @end
  </code></pre>
  
  <p>when I try to add an object to the array  </p>
  
  <pre><code>SharedDataController *sharedDataController = [SharedDataController sharedInstance];
  
  [sharedDataController.qrcodes addObject:result.text];
  NSLog(@"%@", sharedDataController.qrcodes);
  </code></pre>
  
  <p>I get nil, what exactly am I doing wrong?</p>