swiftUI : Updating Text after changes in settings - swiftui

Question

[Edit(1) to reflect posting of streamlined app to illustrate the issue : ].
[Edit (2) : completely removed EnvironmentObject and app now works ! Not understanding WHY body is refreshed as NO #State vars are being modified...Code at end of text]
I am writing an app that, at some point, displays some text, related to the contents of 2 Arrays, depending on a set of rules. These rules can be set in a Settings view, as User's preference.
So, when a user changes the rules he wants applied in Settings, that text needs to be re-assessed.
But of course, things aren't that easy.
I present my settings view as modal on my main ContentView, and when I dismiss that modal, the body of the ContentView is not redrawn...
I created an EnvironmentObject with #Published vars in order to keep track of all the user preferences (that are also written to UserDefaults), and shared that #EnvironmentObject with both my ContentView and SettingsView, in the hope that, being an observedObject, its changes would trigger a refresh of my ContentView.
Not so...
Any ideas to help me go forward on this ? Any pointers would be greatly appreciated (again!).
Posted app on GitHub has following architecture :
An appState EnvironmentObject,
A ContentView that displays a set of texts, depending on some user preferences set in
A settingsView
UserDefaults are initialized in AppDelegate.
Thanks for any help on this...
Content view :
import SwiftUI
struct ContentView: View {
#State var modalIsPresented = false // The "settingsView" modally presented as a sheet
#State private var modalViewCaller = 0 // This triggers the appropriate modal (only one in this example)
var body: some View {
NavigationView {
VStack {
Spacer()
VStack {
Text(generateStrings().text1)
.foregroundColor(Color(UIColor.systemGreen))
Text(generateStrings().text2)
} // end of VStack
.frame(maxWidth: .infinity, alignment: .center)
.lineLimit(nil) // allows unlimited lines
.padding(.all)
Spacer()
} // END of main VStack
.onAppear() {
self.modalViewCaller = 0
}
.navigationBarTitle("Test app", displayMode: .inline)
.navigationBarItems(leading: (
Button(action: {
self.modalViewCaller = 6 // SettingsView
self.modalIsPresented = true
}
) {
Image(systemName: "gear")
.imageScale(.large)
}
))
} // END of NavigationView
.sheet(isPresented: $modalIsPresented, content: sheetContent)
.navigationViewStyle(StackNavigationViewStyle()) // This avoids dual column on iPad
} // END of var body: some View
// MARK: #ViewBuilder func sheetContent() :
#ViewBuilder func sheetContent() -> some View {
if modalViewCaller == 6 {
SettingsView()
}
} // END of func sheetContent
// MARK: generateStrings() : -
func generateStrings() -> (text1: String, text2: String, recapText: String, isHappy: Bool) { // minimumNumberOfEventsCheck
var myBool = false
var aString = "" // The text 1 string
var bString = "" // The text 2 string
var cString = "" // The recap string
if UserDefaults.standard.bool(forKey: kmultiRules) { // The user chose the dual rules option
let ruleSet = UserDefaults.standard.integer(forKey: kruleSelection) + 1
aString = "User chose 2 rules option"
bString = "User chose rule set # \(ruleSet)"
myBool = true
print("isDualRules true loop : generateStrings was called at \(Date().debugDescription)")
cString = "Dual rules option, user chose rule set nb \(ruleSet)"
}
else // The user chose the single rule option
{
aString = "User chose single rule option"
bString = "User had no choice : there is only one set of rules !"
myBool = false
print("isDualRules false loop : generateStrings was called at \(Date().debugDescription)")
cString = "Single rule option, user chose nothing."
}
return (aString, bString, cString, myBool)
} // End of func generatestrings() -> String
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
return ContentView()
}
}
SettingsView :
import SwiftUI
import UIKit
struct SettingsView: View {
#Environment(\.presentationMode) var presentationMode // in order to dismiss the Sheet
#State public var multiRules = UserDefaults.standard.bool(forKey: kmultiRules)
#State private var ruleSelection = UserDefaults.standard.integer(forKey: kruleSelection) // 0 is rule 1, 1 is rule 2
var body: some View {
NavigationView {
List {
Toggle(isOn: $multiRules)
{
Text("more than one rule ?")
}
.padding(.horizontal)
if multiRules {
Picker("", selection: $ruleSelection){
Text("rules 1").tag(0)
Text("rules 2").tag(1)
}.pickerStyle(SegmentedPickerStyle())
.padding(.horizontal)
}
} // End of List
.navigationBarItems(
leading:
Button("Done") {
self.saveDefaults() // We try to save once more if needed
self.presentationMode.wrappedValue.dismiss() // This dismisses the view
}
)
.navigationBarTitle("Settings", displayMode: .inline)
} // END of Navigation view
} // END of some View
func saveDefaults() {
UserDefaults.standard.set(multiRules, forKey: kmultiRules)
UserDefaults.standard.set(ruleSelection, forKey: kruleSelection)
}
}
// MARK: Preview struct
struct SettingsView_Previews: PreviewProvider {
static var previews: some View {
return SettingsView()
}
}
Constants.swift file :
import Foundation
import SwiftUI
let kmultiRules = "two rules"
let kruleSelection = "rules selection"
let kappStateChanged = "appStateChanged"
AppDelegate :
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
// Override point for customization after application launch.
UserDefaults.standard.register(defaults: [ // We initialize the UserDefaults
"two rules": false,
"rules selection": 0, // 0 is ruel 1, 1 is rule 2
"appStateChanged": false
])
return true
}

Answer 1

If you have a shared #EnvironmentObject with #Published properties in two views, if you change such a property from one view, the other one will be re-execute the body property and the view will be updated.
It really helps to create simple standalone examples - not only for asking here, also for gaining a deeper understanding / getting an idea why it doesn't work in the complex case.
For example:
import SwiftUI
class TextSettings: ObservableObject {
#Published var count: Int = 1
}
struct TextSettingsView: View {
#EnvironmentObject var settings: TextSettings
var body: some View {
Form {
Picker(selection: $settings.count, label:
Text("Text Repeat Count"))
{
ForEach(Array(1...5), id: \.self) { value in
Text(String(value)).tag(value)
}
}
}
}
}
struct TextWithSettingExampleView: View {
#EnvironmentObject var settings: TextSettings
var body: some View {
Text(String(repeating: "Hello ", count: Int(settings.count)))
.navigationBarItems(trailing: NavigationLink("Settings", destination: TextSettingsView()))
}
}
struct TextWithSettingExampleView_Previews: PreviewProvider {
static var previews: some View {
NavigationView {
TextWithSettingExampleView()
}
.environmentObject(TextSettings())
}
}

Answer 2

Not sure I fully understand the question, but I had what I believe might be a similar problem where I never got my contentview to reflect the updates in my observed object when the changes were triggered from a modal. I solved/hacked this by triggering an action in my observed object when dismissing the modal like this:
struct ContentView: View {
//
#State var isPresentingModal = false
var body: some View {
//
.sheet(isPresented: self.$isPresentingModal) {
PresentedModalView()
.onDisappear {
//Do something here
}
}
}
}