load NSView from nib file

view category

extension NSView {
  class func loadWithNibNamed(nibNamed: String, loadClass: AnyObject, tag: Int = 0) -> AnyObject? {
    var topLevelObjects: NSArray?
    
    let nib = NSNib(nibNamed: nibNamed, bundle: NSBundle.mainBundle())!
    nib.instantiateWithOwner(nil, topLevelObjects: &topLevelObjects)
    
    for object: AnyObject in topLevelObjects! {
      
      if(object.isKindOfClass(loadClass.classForCoder)) {
        if(tag != 0) {
          let control = object as! NSControl
          if(control.tag == tag) {
            return object
          }
        }
        else {
          return object
        }
      }
    }
    return nil
  }
}