How to detect live changes on TextField in SwiftUI?

Question

I have a simple TextField that binds to the state 'location' like this,

TextField("Search Location", text: $location)

I want to call a function each time this field changes, something like this:

TextField("Search Location", text: $location) {
   self.autocomplete(location)
}

However this doesn't work. I know that there are callbacks, onEditingChanged - however this only seems to be triggered when the field is focussed.

How can I get this function to call each time the field is updated?

Answer 1

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 location: String = ""

    var body: some View {
        TextField("Your Location", text: $location)
            .onChange(of: location) {
                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:

.onReceive(location.publisher) { 
    print($0)
}

_{**Note that** it returns **the change** instead of the entire value. If you need the behavior the same as the `onChange`, you can use the **combine** and follow the answer provided by @pawello2222.}

Answer 2

Another solution, if you need to work with a ViewModel, could be:

import SwiftUI
import Combine

class ViewModel: ObservableObject {
    @Published var location = "" {
        didSet {
            print("set")
            //do whatever you want
        }
    }
}

struct ContentView: View {
    @ObservedObject var viewModel = ViewModel()

    var body: some View {
        TextField("Search Location", text: $viewModel.location)
    }
}

Answer 3

SwiftUI 1 & 2

Use onReceive:

import Combine
import SwiftUI

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

    var body: some View {
        TextField("Search Location", text: $location)
            .onReceive(Just(location)) { location in
                // print(location)
            }
    }
}

Answer 4

While other answers work might work but this one worked for me where I needed to listen to the text change as well as react to it.

first step create one extension function.

extension Binding {
    func onChange(_ handler: @escaping (Value) -> Void) -> Binding<Value> {
        Binding(
            get: { self.wrappedValue },
            set: { newValue in
                self.wrappedValue = newValue
                handler(newValue)
            }
        )
    }
}

now call change on the binding in TextField something like below.

  TextField("hint", text: $text.onChange({ (value) in
      //do something here
  }))

source : HackingWithSwift

Answer 5

What I found most useful was that TextField has a property that is called onEditingChanged which is called when editing starts and when editing completes.

TextField("Enter song title", text: self.$userData.songs[self.songIndex].name, onEditingChanged: { (changed) in
    if changed {
        print("text edit has begun")
    } else {
        print("committed the change")
        saveSongs(self.userData.songs)
    }
})
    .textFieldStyle(RoundedBorderTextFieldStyle())
    .font(.largeTitle)