Binding a button leads to "Missing argument for parameter in call" error - swift

Question

I'm trying to create a Binding in two views so I can change something on one side and have it reflected on the other.
I basically have:
a circle on both views
a button to change the other view's circle color
and one to go to the other view
It all works fine if I only have a Binding in the "ColorChange2"
view, but when I add a Binding in "ColorChange1" I get into trouble.
It tells me: Missing argument for parameter 'isOn2'.
But when I add isOn2 into ColorChange1() it wants a binding, but if I do ColorChange1(isOn2: $isOn2) it says it can't find '$isOn2' in scope.
I found one solution suggesting to add .constant(true)) into the preview but since it's a constant, it wont change the view like I wanted since it's a constant.
What can I do to make it work?
Code:
struct ColorChange1: View {
#State private var isOn = false
#Binding var isOn2 : Bool
var body: some View {
NavigationView {
VStack {
Circle()
.fill(isOn ? .green : .red)
.frame(width: 100)
Button(action: {
isOn2.toggle()
}, label: {
Text("Change button view 2")
.padding()
})
NavigationLink(destination: {
ColorChange2(isOn: $isOn)
}, label: {
Text("Go to view 2")
})
}
}
}
}
struct ColorChange2: View {
#Binding var isOn : Bool
#State private var isOn2 = false
#Environment(\.dismiss) var dismiss
var body: some View {
VStack {
Circle()
.fill(isOn2 ? .green : .red)
.frame(width: 100)
Button(action: {
isOn.toggle()
}, label: {
Text("Change button view 1")
.padding()
})
Button(action: {
dismiss.callAsFunction()
}, label: {
Text("Go to view 1")
})
}
.navigationBarBackButtonHidden(true)
}
}
struct ColorChange_Previews: PreviewProvider {
static var previews: some View {
// ColorChange(isOn2: .constant(true))
ColorChange1()
}
} ```

Answer 1

You don't need both #Binding value in both screen to connect between screen like that.
#Binding means that get the value in #State of the first view and make a connection in the second view. In this scenero, when you go back from second view, it was dismissed.
For your problem, make an ObservableObject to store value. 1 for present in first view and 1 for second view. Then add it to second view when ever you need to display.
Code will be like this
class ColorModel : ObservableObject {
#Published var isOnFirstView = false
#Published var isOnSecondView = false
func didTapChangeColor(atFirstView: Bool) {
if atFirstView {
isOnSecondView = !isOnSecondView
} else {
isOnFirstView = !isOnFirstView
}
}
}
struct ColorChange2: View {
// binding model
#ObservedObject var colorModel : ColorModel
#Environment(\.dismiss) var dismiss
var body: some View {
VStack {
Circle()
.fill(colorModel.isOnSecondView ? .green : .red)
.frame(width: 100)
Button(action: {
colorModel.didTapChangeColor(atFirstView: false)
}, label: {
Text("Change button view 1")
.padding()
})
Button(action: {
dismiss.callAsFunction()
}, label: {
Text("Go to view 1")
})
}
.navigationBarBackButtonHidden(true)
}
}
struct ColorChange1: View {
#StateObject private var colorModel = ColorModel()
var body: some View {
NavigationView {
VStack {
Circle()
.fill(colorModel.isOnFirstView ? .green : .red)
.frame(width: 100)
Button(action: {
colorModel.didTapChangeColor(atFirstView: true)
}, label: {
Text("Change button view 2")
.padding()
})
NavigationLink(destination: {
ColorChange2(colorModel: colorModel)
}, label: {
Text("Go to view 2")
})
}
}
}
}
struct ColorChange_Previews: PreviewProvider {
static var previews: some View {
ColorChange1()
}
}