SwifUI : pass a stored value (via user defaults) to another view - swift

Question

I used user defaults to save the values from a form. I wish to pass one of those values ("nationality") to another view.
I tried using the view model in order to do so, but I get an empty value in the text where I wish to pass this data.
first here is a look at the form
import SwiftUI
struct ProfilePageView: View {
#ObservedObject var viewModel = ViewModel()
var body: some View {
Form {
Section(header: Text("Personal Ifo")) {
TextField("User Name", text: $viewModel.userName)
}
//
Section(header: Text("Your Nationality")) {
Picker(selection: $viewModel.nationality, label: Text("You were born in")) {
ForEach(viewModel.nationalities, id: \.self) { nationality in
Text(nationality)
}
}
} //nationality section end
//
Section(header: Text("Country of residence")) {
Picker(selection: $viewModel.countryOfResidence, label: Text("Where do you live ?")) {
ForEach(viewModel.countriesOfResidence, id: \.self) { residence in
Text(residence)
}
}
} // country of residence section end
//
}
.navigationTitle("Profile")
//form end
}
}
second here is my view model, which enables me to save the form values to user default
import Foundation
class ViewModel: ObservableObject {
#Published var userName: String {
didSet {
UserDefaults.standard.setValue(userName, forKey: "username")
}
}
//nationality
#Published var nationality: String {
didSet {
UserDefaults.standard.setValue(nationality, forKey: "nationality")
}
}
public var nationalities = ["USA", "Japan", "Senegal", "France"]
//country of residence
#Published var countryOfResidence: String {
didSet {
UserDefaults.standard.setValue(countryOfResidence, forKey: "country of residence")
}
}
public var countriesOfResidence = ["USA", "Japan", "Senegal", "France"]
init() {
self.userName = UserDefaults.standard.object(forKey: "username") as? String ?? ""
self.nationality = UserDefaults.standard.object(forKey: "nationality") as? String ?? ""
self.countryOfResidence = UserDefaults.standard.object(forKey: "Coutry of residence") as? String ?? ""
}
}
finally here is the view where I wish to attach this value. I am using #observedObject in order to try an retrieve the "nationality" value from my view model. however the value is not passed in the text
import SwiftUI
struct VisaPolicyDetailView: View {
#Binding var country: Country
#ObservedObject var viewmodel = ViewModel()
var body: some View {
VStack(alignment: .leading,spacing: 20) {
//a dismiss button
HStack {
Spacer()
Image(systemName: "xmark")
.renderingMode(.original)
.resizable()
.aspectRatio(contentMode: .fit)
.frame(width: 40, height: 40)
}
Spacer()
Text(country.countryName)
.font(.title)
.fontWeight(.medium)
Text("Visa policy for \(viewmodel.nationality) : visa policy")
.font(.title2)
Spacer()
}
.padding()
.navigationTitle("Visa Policy Detail")
}
}

Answer 1

In the provided scenario it is better to use shared ViewModel, like
class ViewModel: ObservableObject {
static let shared = ViewModel()
// .. other code
}
and use that shared in all affected views
struct ProfilePageView: View {
#ObservedObject var viewModel = ViewModel.shared // << here !!
...
and
struct VisaPolicyDetailView: View {
#Binding var country: Country
#ObservedObject var viewmodel = ViewModel.shared // << here !!
...
then both views will observe same instance of ViewModel.
SwiftUI 2.0: use AppStorage to automatically store/observe user defaults, like
#AppStorage("nationality") var nationality = "some default here"