title: Auto property synthesis (@property) and inheritance
body: <p>With XCode 5.1, a new warning appears. It made me understand <em>-obviously-</em> that I was doing something wrong.</p>
  
  <p>The idea was to have an object (a model) and it's mutable version which inherits from the original class. So the idea is to open a property which was <code>readonly</code> to <code>readwrite</code></p>
  
  <pre><code>@interface Car : NSObject
      @property (strong, readonly) NSString *name;
  @end
  
  @interface MutableCar : Car
      @property (strong, readwrite) NSString *name;
  @end
  </code></pre>
  
  <p>Those needs to be in separate files (like two normal classes).</p>
  
  <p>And it gives this warning :</p>
  
  <pre class="lang-none prettyprint-override"><code>Auto property synthesis will not synthesize property 'name' because it is 'readwrite' but it will be synthesized 'readonly' via another property
  </code></pre>
  
  <p>So I would like to know what is the right solution to do something like it, if it's even possible. if it's needed to write accessors and avoid using auto synthesis, etc. Just please be precise and support your answer with documentation or whatever.</p>