How can a UITextView listen on its own changes without delegate

Question

I am making a custom UITextView subclass. The purpose is to support a placeholder, not natively supported for UITextView. The text view needs to listen on its own changes in order to show / hide the placeholder label. But I cannot use a delegate because the user class might reset the delegate to itself. How can I achieve this without any delegate methods?

Answer 1

It seems a little strange that you can't use a delegate , and it might be worth checking there's not a better architecture that would allow it, but if it's not feasible you could use notifications to alert you to activity in the textView .

TextViews issue textDidBeginEditingNotification , textDidChangeNotification , and textDidEndEditingNotification .

You could subscribe to these notifications, compare the text value against a stored version, and respond accordingly.

Details on this page: Apple docs for textView notifications

Answer 2

You can listen for the text value's changes, and act upon it. If there is at least one character, then we hide the placeholder, if there are 0 characters, we unhide the placeholder.

class CustomTextView: UITextView {

   override var text: String! {
        didSet (newValue) {
            let shouldHide = newValue.count > 0
            placeholder.isHidden = shouldHide
        }
    }
}

Answer 3

But I cannot use a delegate because the user class might reset the delegate to itself. How can I achieve this without any delegate methods?

Why would it do that? Have you placed YourTextView.delegate = self in multiple places? Have you already tried delegates?

This is the code for Delegates:

func textViewDidEndEditing(_ textView: UITextView) {

}

If you really don't want to use delegates you could use a timer that checks the textview very frequently and compares it to a previous value that you store. You could also check for keyboard actions and then checks the textview.

let timer = Timer(timeInterval: 0.0, repeats: true) { _ in 
 //put a conditional here that compares the textview text to the previously stored value
 }