If I want to handle changes to a UITextField, such as the user typing in it; it seems like this can be done either by assigning a delegate to that text field, and then having the delegate implement shouldChangeCharactersInRange, or by adding a target to the textField, and handling the UIControlEventEditingChanged event.
Aside from the fact that with the delegate method, you can return NO and therefor stop the user from making the edit, is there any difference between these 2 things?
Same question for handling the beginning of editing or the ending of editing. It could be done either with the appropriate delegate methods or with the appropriate events. What is the textField delegate actually for if the control events can do the necessary work?
You're right; you can essentially do the same thing via both, but UIControl is lower level and lets you siphon off each particular UIEvent to different targets via [UIControl addTarget:action:forControlEvents:] where as there is only a single delegate.
I would also say that the UITextField delegate protocol is simply there as a more convenient, higher level alternative to UIControl/UIEvent as a way to manage the behaviour of a UITextField.
The most common delegate pattern is UITableView DataSource and Delegate and I would say that using the UITextField delegate protocol is quite similar and therefore looks far more straight forward with more defined intentions than handing the messages from UIControl directly.