title: iOS __kindof NSArray?
body: <p>I've been checking out iOS 9 new features as a developer and some of them like the StackView look awesome. </p>
  
  <p>When I went the the header file of UIStackView I saw this:</p>
  
  <pre><code>@property(nonatomic,readonly,copy) NSArray&lt;__kindof UIView *&gt; *arrangedSubviews;
  </code></pre>
  
  <p>What is the __kindof on NSArray*. Are we able to specify a type on a NSArray * now? </p>
  
  <p>Little test:</p>
  
  <pre><code>@interface DXTEST ()
  @property (strong, nonatomic) NSMutableArray &lt;__kindof NSString *&gt;  *strings;
  @end
  
  @implementation DXTEST
  
  - ( instancetype ) init {
      self = [super init];
  
      if( self ) {
          _strings = [NSMutableArray new];
  
          [_strings addObject:@(1)]; &lt;-- compiler warning wieeeeee
      }
  
      return self;
  }
  
  @end
  </code></pre>