How to attach subscriber to State or Binding in SwiftUI/Combine?

Question

With a Combine Publisher, I can use the following to call a closure whenever a value changes:

let cancellable = x.sink { value in … }

How can I achieve the same behaviour with a variable marked @State or @Binding?

@JoakimDanielson I was under the false impression that willSet/didSet do not work on property wrappers. If you make your comment into an answer, I will gladly accept! — Div, Sep 12 '20 at 20:03
What are you trying to achieve by doing that? Who would subscribe to that if you could achieve that — New Dev, Sep 12 '20 at 21:52
@NewDev Being able to subscribe to a State variable allows for both View code and non-View code to receive updates on the value. — Div, Sep 14 '20 at 21:52

Joakim Danielson · Accepted Answer · 2022-04-13T21:05:36.910

3

Update

The below answer doesn't seem to work anymore, instead one can use .onChange(of:) instead on the property

.onChange(of: someProperty) { value in
    //use new value for someProperty
 }

You can use willSet and didSet as with any normal property

@State private var someProperty: String {
    didSet {

    }

    willSet {

    }
}

edited Apr 13 '22 at 21:05

answered Sep 12 '20 at 20:17

Joakim Danielson

1

This is not called for some reason. I'm using Picker and binding of @State variable. – atereshkov Jan 17 '21 at 19:29
@atereshkov Yes this seems to have changed, you should look into using `.onChange(of: perform)`instead – Joakim Danielson Jan 18 '21 at 12:31
`.onChange(of: myPropertyName) { newValue in }` should be used on particular view instead of `didSet { }` on particular property in SwiftUI – Danil Oct 22 '22 at 19:10

1 Answers1