.toggle() function on bool 不调用 didSet。 这是一个错误吗？

Question

I have a @State Bool variable with didSet on it. I want to do something when the variable change therefore I have tried to use didSet. The problem is when I use the.toggle() function to toggle the state of the bool, didSet is not called.

Take this code for example:

import SwiftUI

struct SwiftUIView: View {
    @State var testBool = false {
        didSet {
            print("set")
        }
    }
    var body: some View {
        VStack {
            Button(action: {
                self.testBool.toggle()
            }) {
                Text("Toggle with .toggle()")
            }

            Button(action: {
                if self.testBool {
                    self.testBool = false
                } else {
                    self.testBool = true
                }
            }) {
                Text("Toggle with if")
            }
        }
    }
}

struct SwiftUIView_Previews: PreviewProvider {
    static var previews: some View {
        SwiftUIView()
    }
}

All I have is 2 buttons: - One button toggles the state of the bool using the.toggle() function. - The next button toggles the state using a basic if/else

The top button using the.toggle() function does not print “set” in the console as expected with the didSet on the variable. The bottom button does as expected.

Answer 1

This is a known compiler regression SR-12407 . It will be probably fixed in next Xcode version.