title: Understanding weak reference
body: <p>I have the following ARC enabled code</p>
  
  <pre><code>@property (nonatomic, weak) NSArray *a;
  - (void)viewDidLoad
  {
      [super viewDidLoad];
      self.a = @[@1, @2];
      NSLog(@"ab is %@", self.a); //prints details of array
      // Do any additional setup after loading the view, typically from a nib.
  }
  - (void)didReceiveMemoryWarning
  {
  
      [super didReceiveMemoryWarning];
      for (id element in self.a) { //empty here
          NSLog(@"blah");
      }
      // Dispose of any resources that can be recreated.
  }
  </code></pre>
  
  <p>This is the only place where I used the <code>self.a</code>. This is a test program I wrote to debug one of my issues.</p>
  
  <p>When I simulate memory warning <code>self.a</code> vanishes? Why?</p>