title: Cannot increment a number in swift
body: <p>I have a variable populated from a keystore, that when incremented, gives an error that reads: 
  <strong>"NSNumber is not convertible to @lvalue UIint8"</strong></p>
  
  <pre><code>if let bankbalance: AnyObject? = keystore.objectForKey("coinbalance"){
     let mybalance = bankbalance as NSNumber
      mybalance += 50 //this line gives the error 
  }
  </code></pre>
  
  <p>My question is what is convertible to UIint8 so that I can add to my variable? I've tried INT, Float, double.</p>