textField:shouldChangeCharactersInRange:replacementString vs. UITextFieldTextDidChangeNotification

I'm building a Passcode Lock view, and I want to set the text to a dot on one of the four box labels when a user enters a new charact开发者_StackOverflower into the text field.

Should I use textField:shouldChangeCharactersInRange:replacementString or UITextFieldTextDidChangeNotification?

Using textField:shouldChangeCharactersInRange:replacementString seems easier, but shouldChangeCharactersInRange seems more correct.

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I’d recommend using the delegate method, rather than the notification. Another option: set the text fields’ secureTextEntry property to YES. (See the documentation for the UITextInputTraits protocol, which UITextField conforms to).