title: Objective-C property alias
body: <p>Let's say that <code>ParentClass</code> has a string property called <code>a</code>:</p>
  
  <p><code>@property (nonatomic, strong) NSString *a;</code></p>
  
  <p>In a subclass <code>ChildClass</code>, I want the property <code>b</code> to be an alias for <code>super.a</code>. Meaning <code>b</code> does not really hold any value in itself, it just points to <code>a</code>.
  If the value of <code>a</code> changes, then it should be reflected in <code>b</code>, and vice-versa.</p>
  
  <p>What the the cleanest way to achieve this in Objective-C.</p>