CommentsTableViewBackgroundView.swift

class CommentsTableViewBackgroundView: UIView {
  
  dynamic var isEmpty = true
  dynamic var isLoading = false
  
  let activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .WhiteLarge)
  
  lazy var label: UILabel = {
    let label = UILabel()
    label.text = "No comments yet. Be the first one!"
    label.numberOfLines = 0
    label.textColor = UIColor.eoDarkGrayText()
    label.textAlignment = .Center
    return label
  }()
  
  convenience override init() {
    self.init(frame: CGRectZero)
    setupViews()
    setupLayout()
    setupBindings()
  }
  
  func setupViews() {
    addSubview(activityIndicator)
    addSubview(label)
  }
  
  func setupLayout() {
    activityIndicator.alignCenterYWithView(self, predicate: "*1.3")
    activityIndicator.alignCenterXWithView(self, predicate: "0")
    label.alignCenterWithView(activityIndicator)
    label.alignLeading("20", trailing: "-20", toView: self)
  }
  
  func setupBindings() {
    let isLoadingSignal = RACObserve(self, "isLoading")
    let isEmptySignal = RACObserve(self, "isEmpty")
    
    let showEmptyLabelSignal = isEmptySignal
      .combineLatestWith(isLoadingSignal)
      .map { (tuple) -> AnyObject! in
        let tuple = tuple as RACTuple
        return (tuple.first as Bool) && !(tuple.second as Bool)
      }
    
    RAC(activityIndicator, "hidden") <~ isLoadingSignal.not()
    RAC(label, "hidden") <~ showEmptyLabelSignal.not()
    
    isLoadingSignal.subscribeNext { [weak self] (object) -> () in
      if let a = self?.activityIndicator {
        (object as Bool) ? a.startAnimating() : a.stopAnimating()
      }
    }
    
  }

}