How to toggle a UITextField secure text entry (hide password) in Swift?

Question

I currently have a UITextfield with an eye icon in it that when pressed is supposed to toggle the secure text entry on and off.

I know you can che

Answer 1

An unintended side-effect of this is that if the user toggles to insecure, and then back to secure, the existing text will be cleared if the user continues typing. The cursor may also end up in the wrong position unless we reset the selected text range.

Below is an implementation that handles these cases (Swift 4)

extension UITextField {
    func togglePasswordVisibility() {
        isSecureTextEntry = !isSecureTextEntry

        if let existingText = text, isSecureTextEntry {
            /* When toggling to secure text, all text will be purged if the user 
             continues typing unless we intervene. This is prevented by first 
             deleting the existing text and then recovering the original text. */
            deleteBackward()

            if let textRange = textRange(from: beginningOfDocument, to: endOfDocument) {
                replace(textRange, withText: existingText)
            }
        }

        /* Reset the selected text range since the cursor can end up in the wrong
         position after a toggle because the text might vary in width */
        if let existingSelectedTextRange = selectedTextRange {
            selectedTextRange = nil
            selectedTextRange = existingSelectedTextRange
        }
    }
}

This snippet is using the replace(_:withText:) function because it triggers the .editingChanged event, which happens to be useful in my application. Just setting text = existingText should be fine as well.