Why RxCocoa didn't provide subscribe for UILabel's text change?

Question

RxCocoa provide subscribe for UITextField and UITextView text change:

UITextField().rx.text.orEmpty.changed
    .subscribe { text in
        print(text)
    }
    .disposed(by: disposeBag)

UITextView().rx.text.changed.subscribe { t in
    print(t)
}.disposed(by: disposeBag)

But no convenience for UILabel:

UILabel().rx.text.subscribe ...

Why rxcocoa designed for this?

Answer 1

In essence, the text method is a wrapper around the UIControl's addTarget(:action:for:) method. It turns that method into something that is Observable.

The UILabel type isn't derived from UIControl and so doesn't have an addTarget(:action:for:) method. You can't attach an @IBAction to a UILabel in normal UIKit, so you can't attach an Rx ControlProperty to a UILabel either.

And just like in UIKit, you don't need to observe changes to a UILabel because the only way it changes is if your code changed it. Just observe the thing that triggered the label to change instead.

---

It will help to understand if you look at the code... The text method is just a rename of the value method:

public var text: ControlProperty<String?> {
    value
}

and the value method is a ControlProperty that monitors the "default events".

    public var value: ControlProperty<String?> {
        return base.rx.controlPropertyWithDefaultEvents(

Looking at controlPropertyWithDefaultEvents, we can find out what the default events are:

internal func controlPropertyWithDefaultEvents<T>(
    editingEvents: UIControl.Event = [.allEditingEvents, .valueChanged],
    getter: @escaping (Base) -> T,
    setter: @escaping (Base, T) -> Void
    ) -> ControlProperty<T>