title: Find delegate in a swift Array of delegates
body: <p>I want to check if I already have a delegate in my removeDelegate method before removing.
  How do I do that? </p>
  
  <p>Here's what I've got so far:</p>
  
  <pre><code>protocol LocationManagerDelegate {
      func locationManagerDidUpdateLocation(
          oldLocation: CLLocationCoordinate2D,
          currentLocation: CLLocationCoordinate2D
      )
  }
  
  class LocationManager: NSObject {
      private var _delegates = [LocationManagerDelegate]()
  
      func removeDelegate(delegate:LocationManagerDelegate) {
          if contains(_delegates, delegate) {
              // Remove delegate
          }
      }
  }
  </code></pre>
  
  <p>However, this gives me the following error on the 'if contains' line: </p>
  
  <p>cannot invoke 'contains' with an argument list of type '(@lvalue Array&lt; LocationManagerDelegate >!, LocationManagerDelegate)'</p>