isFirstResponder observable with RxSwift

UIView+Rx.swift

import RxCocoa
import RxSwift
import UIKit

extension Reactive where Base: UIView {
    var isFirstResponder: Observable<Bool> {
        return Observable
            .merge(
                methodInvoked(#selector(UIView.becomeFirstResponder)),
                methodInvoked(#selector(UIView.resignFirstResponder))
            )
            .map{ [weak view = self.base] _ in
                view?.isFirstResponder ?? false
            }
            .startWith(base.isFirstResponder)
            .distinctUntilChanged()
            .share(replay: 1)
    }
}

It doesn't work.

I haven't used this in quite a while. It worked at the time. What does not work?

Seems to work for me...

Works fine for me, thanks!

This has stopped working in iOS 18, causing a stack overflow inside -[UITextInputUIResponderAccessibility becomeFirstResponder]

I wish isFirstResponder was backed by KVO, we'd simply used this:

extension Reactive where Base: UIResponder {
    var isFirstResponder: Observable<Bool> {
        return observe(\.isFirstResponder)
            .distinctUntilChanged()
    }
}

However, UIKit's views do not properly support KVO for isFirstResponder, so I had to re-enable it by overriding becomeFirstResponder and resignFirstResponder in every subclass that needs to be observed via rx.isFirstResponder:

override func becomeFirstResponder() -> Bool {
    willChangeValue(for: \.isFirstResponder)
    let result = super.becomeFirstResponder()
    didChangeValue(for: \.isFirstResponder)
    return result
}

override func resignFirstResponder() -> Bool {
    willChangeValue(for: \.isFirstResponder)
    let result = super.resignFirstResponder()
    didChangeValue(for: \.isFirstResponder)
    return result
}