The method of Swift3 listening to the change of UITextView text in iOS development three methods of of

In addition to UITextField, UITextView is often used in the project, so it is inevitable that there will be a need to monitor the amount of text in the UITextView text box. Here are two common ways in swift3

Mode 1: Global notification

1. Notice of Registration

Register in place to listen for global notifications of UITextView text changes

//UITextView  Two methods of listening for starting input 
// Method 1: Notice 
NotificationCenter.default.addObserver(self, selector: #selector(ComposeVC.textViewChange), name: NSNotification.Name.UITextViewTextDidChange, object: nil)

2. Implement the listening method here named textViewChange

@objc fileprivate func textViewChange() {
XWLog("textView Text change  :\(composeTextView.text)")
}

3. Don't forget the ecstasy notification in the controller

// Remove notification 
deinit {
NotificationCenter.default.removeObserver(self)
}

Mode 2: Proxy

1. Set up the proxy

//1. Set up proxy 
composeTextView.delegate = self

2. Follow the proxy protocol and implement the proxy method

//MARK: - TEXTVIEW DELEGATE
extension ComposeVC : UITextViewDelegate {
func textViewDidChange(_ textView: UITextView) {
if textView.text.lengthOfBytes(using: .utf8) > 0 {
// Text box with more than one text 0  Perform corresponding operations 
}else{
// The number of words in the text box is equal to 0  Perform corresponding operations 
}
}
}