title: Realm.io - Compound primary key in objective-c
body: <p>I'm struggling to find a way of combining multiple properties into a primary key, using Realm.io and Objective-c.</p>
  
  <p>Take this object as an example:</p>
  
  <pre><code>@interface Beacon : RLMObject
  
  @property NSString *uuid;
  @property int major;
  @property int minor;
  
  @end
  
  RLM_ARRAY_TYPE(Beacon)
  </code></pre>
  
  <p>How would I then combine e.g. uuid, major, and minor into a single primary key?</p>