How to change state of SwiftUI Toggle externally - swiftui

Question

I am trying to change the state of a Toggle from outside the view. I've tried ObservableObject and EnvironmentObject, but the toggle is expecting a Binding (#State).
I need to execute a callback when the user taps the toggle
I need to change the state of the toggle programmatically w/o executing the callback.
I am using a shared model for this and other views, ideally I'd like to be able to use that for an 'enabled' Bool to take the place of the State var isOn.
This code does let me execute the callback via the extension, but I cannot figure out how to change the State variable isOn externally, and if I was able to, I'm guessing my callback would be executed, which I don't want to happen.
import SwiftUI
struct ControlView: View {
var title: String
var panel: Int
var callback: ()-> Void
#State public var isOn = false // toggle state
#EnvironmentObject var state: MainViewModel
//#ViewBuilder
var body: some View {
VStack() {
// -- Header
HStack() {
Text(" ")
Image(self.state.panelIcon(panel: panel)).resizable().frame(width: 13.0, height: 13.0)
Text(title)
Spacer()
}.padding(EdgeInsets(top: 8, leading: 0, bottom: 8, trailing: 0))
.background(Color(red: 0.9, green: 0.9, blue: 0.9))
// -- Switch
Toggle(isOn: $isOn.didSet { (state) in
// Activate ARC
callback()
}) {
Text("Enable ARC")
}.padding(EdgeInsets(top: 0, leading: 12, bottom: 10, trailing: 12))
}.overlay(
RoundedRectangle(cornerRadius: 10)
.stroke(Color(red: 0.8, green: 0.8, blue: 0.8), lineWidth: 1.25)
).background(Color.white)
}
}
extension Binding {
func didSet(execute: #escaping (Value) -> Void) -> Binding {
return Binding(
get: { self.wrappedValue },
set: {
self.wrappedValue = $0
execute($0)
}
)
}
}

Answer 1

You're on the right track by creating a custom Binding with a set function that performs your side effect. But instead of using a State, create a custom Binding that directly modifies the enabled property of your ObservableObject. Example:
import PlaygroundSupport
import SwiftUI
class MyModel: ObservableObject {
#Published var enabled: Bool = false
#Published var sideEffectCount: Int = 0
}
struct RootView: View {
#EnvironmentObject var model: MyModel
var body: some View {
List {
Text("Side effect count: \(model.sideEffectCount)")
Button("Set to false programmatically") {
model.enabled = false
}
Button("Set to true programmatically") {
model.enabled = true
}
Toggle("Toggle without side effect", isOn: $model.enabled)
Toggle("Toggle WITH side effect", isOn: Binding(
get: { model.enabled },
set: { newValue in
withAnimation {
if newValue {
model.sideEffectCount += 1
}
model.enabled = newValue
}
}
))
}
}
}
PlaygroundPage.current.setLiveView(
RootView()
.environmentObject(MyModel())
)

Answer 2

You can use onChange to trigger a side effect as the result of a value changing, such as a Binding. e.g.
.onChange(of:isOn) { [isOn] newValue in
if newValue {
model.sideEffectCount += 1
}
model.enabled = newValue
}