Question 67898 in IOS Swift Question posted in
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.onChange(of: ) for multiple @State properties at once? – Ios swift

Is there a way I can use .onChange to detect the change of multiple @State properties at once? I know I could just chain 2 .onChange modifiers but it would be better if I could just detect all at once and run some code.

@State private var width = 0.0
@State private var height = 0.0

var body: some View {
    Button(action: {
        width += 0.1
    }, label: {
        Text("Width + 0.1")
    })
    .onChange(of: width) { _ in 
        print("Changed")
    }
}
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2

Answers


  1. 0

    For this case here is the simplest I think

    .onChange(of: width + height) { _ in
    print("Changed")
}

    Update: as I wrote above is ‘simplest’ (and for specific scenarios can be enough), but of course other variants, "more smart/heavy/generic/etc", are also available.

    Thanks to @AgentBilly, here is one of them:

    .onChange(of: [width, height]) { _ in
    print("Changed")
}
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  2. 0

    Create a struct and use that as your state:

    struct Size {
  var width: Double = 0 
  var height: Double = 0

  // mutating func exampleMethod(){
  // }
}

    Then init it as your state:

    @State var size = Size()

var body: some View {
    Button(action: {
        size.width += 0.1
    }) {
        Text("Width + 0.1")
    }
    .onChange(of: size) { newSize in 
        print("Changed")
    }
}
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