title: How to declare NSString constants for passing to NSNotificationCenter
body: <p>I've got the following in my .h file:</p>
  
  <pre><code>#ifndef _BALANCE_NOTIFICATION
  #define _BALANCE NOTIFICATION
  const NSString *BalanceUpdateNotification
  #endif
  </code></pre>
  
  <p>and the following in my .m file:</p>
  
  <pre><code>const NSString *BalanceUpdateNotification = @"BalanceUpdateNotification";
  </code></pre>
  
  <p>I'm using this with the following codes:</p>
  
  <pre><code>[[NSNotificationCenter defaultCenter]
      addObserver:self
      selector:@selector(updateBalance:)
      name:BalanceUpdateNotification
      object:nil];
  </code></pre>
  
  <p>and</p>
  
  <pre><code>[[NSNotificatoinCenter defaultCenter]
      postNotificationName:BalanceUpdateNotification
      object:self userInfo:nil];
  </code></pre>
  
  <p>Which works, but it gives me a warning:</p>
  
  <pre><code>Passing argument 1 of 'postNotificationName:object:userInfo' discards qualifiers from pointer target type
  </code></pre>
  
  <p>So, I can cast it to (NSString *), but I'm wondering what the proper way to do this is.</p>