swift3.0使用ReactiveCocoa做textView的一个placeHolder隐藏

首先导入ReactiveCocoa

let textView = UITextView()
let placeHolder = UILabel()
_ =  textView.reactive.continuousTextValues.observeResult(
{ (result) in
     if ((textView.text.characters.count) > 0) {
          placeHolder.isHidden = true
        }else
        {
          placeHolder.isHidden = false
        }
 })

相比于之前设置代理来实现方便的多