UITextField text change event

Question

How can I detect any text changes in a textField? The delegate method shouldChangeCharactersInRange works for something, but it did not fulfill my need exactly.

Answer 1

Swift Version tested:

//Somewhere in your UIViewController, like viewDidLoad(){ ... }
self.textField.addTarget(
        self, 
        action: #selector(SearchViewController.textFieldDidChange(_:)),
        forControlEvents: UIControlEvents.EditingChanged
)

Parameters explained:

self.textField //-> A UITextField defined somewhere in your UIViewController
self //-> UIViewController
.textFieldDidChange(_:) //-> Can be named anyway you like, as long as it is defined in your UIViewController

Then add the method you created above in your UIViewController:

//Gets called everytime the text changes in the textfield.
func textFieldDidChange(textField: UITextField){

    print("Text changed: " + textField.text!)

}

Answer 2

Swift 4 Version

Using Key-Value Observing Notify objects about changes to the properties of other objects.

var textFieldObserver: NSKeyValueObservation?

textFieldObserver = yourTextField.observe(\.text, options: [.new, .old]) { [weak self] (object, changeValue) in
  guard let strongSelf = self else { return }
  print(changeValue)
}

Answer 3

SwiftUI

If you are using the native SwiftUI TextField or just using the UIKit UITextField (here is how), you can observe for text changes like:

SwiftUI 2.0

From iOS 14, macOS 11, or any other OS contains SwiftUI 2.0, there is a new modifier called .onChange that detects any change of the given state:

struct ContentView: View {
    @State var text: String = ""

    var body: some View {
        TextField("Enter text here", text: $text)
            .onChange(of: text) {
                print($0) // You can do anything due to the change here.
                // self.autocomplete($0) // like this
            }
    }
}

SwiftUI 1.0

For older iOS and other SwiftUI 1.0 platforms, you can use onReceive with the help of the combine framework:

import Combine

.onReceive(Just(text)) { 
    print($0)
}

_{Note that you can use text.publisher instead of Just(text) but it returns the change instead of the entire value.}