Passing state between 2 pages SwiftUI - swift

Question

I'm trying to re create an older version of my Onboarding setup with the new SwiftUI and when I try to share the state so the view changes, it simply doesn't know that something has changed, this is what I'm doing:
In the main .swift struct (not ContentView.swift) I defined the pages like this:
#main
struct AnotherAPP: App {
#ObservedObject var onBoardingUserDefaults = OnBoardingUserDefaults()
let persistenceController = PersistenceController.shared
var body: some Scene {
WindowGroup {
// Onboarding screen
if (onBoardingUserDefaults.isOnBoardingDone == false) {
OnboardingPageView()
} else {
UserLoginView()
}
}
}
}
So on the onBoarding page when I click the button to go to the login, it stores it, but it doesn't actually refreshes the view. There (in the OnboardingPageView.swift) I call the UserDefaults like this:
#ObservedObject private var onBoardingUserDefaults = OnBoardingUserDefaults()
and on the button I change it like this:
self.onBoardingUserDefaults.isOnBoardingDone = true
UserDefaults.standard.synchronize()
So what's going on?
I know for instance if I create a #State on the #main and I bind it to the OnboardingPageView it works, as soon as I hit that button it takes me there.

Answer 1

You can use AppStorage to manage UserDefaults variable in multiple views:
#main
struct TestApp: App {
#AppStorage("isOnBoardingDone") var isOnBoardingDone = false
var body: some Scene {
WindowGroup {
if !isOnBoardingDone {
OnboardingPageView(isOnBoardingDone: $isOnBoardingDone)
} else {
UserLoginView()
}
}
}
}
struct OnboardingPageView: View {
#Binding var isOnBoardingDone: Bool
var body: some View {
Button("Complete") {
isOnBoardingDone = true
}
}
}

Answer 2

If I understood correctly, you are trying to pass the value of a state variable in the Content View to another view in the same app. For simplicity, Let's say your variable is initialised as follows in ContentView:
#State private var countryIndex = 0 //Assuming the name of the variable is countryIndex
Now, to transfer the value write the following in the Content View (or wherever the variable is initially):
//Other code
NavigationLink(destination: NextPage(valueFromContentView: $countryIndex)) {
Text("Moving On")
}//In this case, the variable that will store the value of countryIndex in the other view is called valueFromContentView
//Close your VStacks and your body and content view with a '}'
In your second view or the other view, initialise a Binding variable called valueFromContentView using:
#Binding var valueFromContentView: Int
Then, scroll down to the code that creates your previews. FYI, It is another struct called ViewName_Previews: PreviewProvider { ... }
IF you haven't changed anything, it will be:
struct NextPage_Previews: PreviewProvider {
static var previews: some View {
}
}
Remember, my second view is called NextPage.
Inside the previews braces, enter the code:
NextPage(valueFromContentView: .constant(0))
So, the code that creates the preview for your application now looks like:
struct NextPage_Previews: PreviewProvider {
static var previews: some View {
NextPage(valueFromContentView: .constant(0)) //This is what you add
}
}
Remember, NextPage is the name of my view and valueFromContentView is teh binding variable that I initialised above
Like this, you now can transfer the value of a variable in one view to another view.