Check out example codes for "textchange in textview swift". It will help you in understanding the concepts better.

Code Example 1

class ViewController: UIViewController, UITextViewDelegate { //If your class is not conforms to the UITextViewDelegate protocol you will not be able to set it as delegate to UITextView

    @IBOutlet weak var bodyText: UITextView!

    override func viewDidLoad() {
        bodyText.delegate = self //Without setting the delegate you won't be able to track UITextView events

    func textViewDidChange(_ textView: UITextView) { //Handle the text changes here
        print(textView.text); //the textView parameter is the textView where text was changed

Learn ReactJs, React Native from