How to detect the change of UITextField when the button tapped

Question

I'm observing a textfield using combine like this.

extension UITextField {

    var textPublisher: AnyPublisher<String, Never> {
        NotificationCenter.default.publisher(
            for: UITextField.textDidChangeNotification,
            object: self
        )
        .compactMap { ($0.object as? UITextField)?.text }
        .eraseToAnyPublisher()
    }

}

(source code from https://cocoacasts.com/combine-fundamentals-observing-a-text-field-with-combine )

And I have a button that make textfield's text nil when pressed.
textPublisher detect keyboard input very well, but when the button is pressed, it doesn't publish anything.

How can I detect the textfield's change when the button pressed?

Answer 1

The text field notification is only broadcast (by default) when the user makes changes. When you make programmatic changes, however, you can simply broadcast the notification yourself.

Here is a Playground. Note that the button action simply uses NotificationCenter.default.post(name:object:) :

import UIKit
import PlaygroundSupport
import Combine

extension UITextField {
    
    var textPublisher: AnyPublisher<String, Never> {
        NotificationCenter.default.publisher(
            for: UITextField.textDidChangeNotification,
            object: self
        )
        .compactMap { ($0.object as? UITextField)?.text }
        .eraseToAnyPublisher()
    }
}

let controller = UIViewController()
controller.view.frame = CGRect(x: 0, y: 0, width: 340, height: 480)

let textField = UITextField(frame: CGRect(x: 20, y: 20, width: 300, height: 30))
controller.view.addSubview(textField)
textField.borderStyle = .line

let button = UIButton(frame: CGRect(x:20, y: 70, width: 200, height: 30), primaryAction: UIAction(title: "Push Me", handler: { action in
    textField.text = ""
    NotificationCenter.default.post(name: UITextField.textDidChangeNotification, object: textField)
}))
button.configuration = .bordered()
controller.view.addSubview(button)

let subscription = textField.textPublisher.sink {
    print("There is new text: \($0)")
}

PlaygroundSupport.PlaygroundPage.current.liveView = controller;