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Using UserDefaults to Persist Settings in SwiftUI

Overview​

In this snippet, we explore how to use SwiftUI's AppStorage to create a settings screen that persists user preferences across app launches. AppStorage simplifies working with UserDefaults while ensuring your UI automatically updates when values change.

Source: 🔗 Using UserDefaults To Persist in SwiftUI

Code Example​

Step 1: Define Static Keys for UserDefaults​

extension String {
    static var settingsUserNameKey: String { "settings.userName" }
    static var settingsUserAddressKey: String { "settings.userAddress" }
    static var settingsUserAdsEnabledKey: String { "settings.isAdsEnabled" }
    static var adPrivacyTypeKey: String { "settings.adPrivacyType" }
}

Step 2: Create a SwiftUI Settings View​

import SwiftUI

struct ContentView: View {
    @AppStorage(wrappedValue: "No userName", .settingsUserNameKey)
    private var userName: String

    @AppStorage(.settingsUserAddressKey)
    private var userAddress: String = ""

    @AppStorage(.settingsUserAdsEnabledKey)
    private var isAdsEnabled: Bool = false

    @AppStorage(.adPrivacyTypeKey)
    private var adPrivacyType: AdPrivacyType = .noTracking

    var body: some View {
        NavigationView {
            Form {
                TextField("Name", text: $userName)
                TextField("Address", text: $userAddress)

                Toggle("Enable Ads", isOn: $isAdsEnabled)

                if isAdsEnabled {
                    Section(header: Text("Advertising Policy")) {
                        Picker("Select Your Policy", selection: $adPrivacyType) {
                            ForEach(AdPrivacyType.allCases) { policy in
                                Text(policy.rawValue).tag(policy)
                            }
                        }
                        .pickerStyle(SegmentedPickerStyle())
                    }
                }
            }
            .navigationBarTitle("User Settings")
        }
    }
}

enum AdPrivacyType: String, CaseIterable, Identifiable {
    case noTracking = "No Tracking"
    case essential = "Only Essential Cookies"
    case full = "Standard Tracking"
    
    var id: String { rawValue }
}

Explanation​

  1. Static Keys for UserDefaults: The extension String centralizes keys to avoid hardcoding across the app.
  2. @AppStorage: This property wrapper automatically synchronizes values with UserDefaults and invalidates the view when values change.
  3. Dynamic UI: The Toggle and Picker demonstrate how changes in AppStorage variables dynamically affect the UI.

Benefits​

  • Ease of Use: Simplifies state management for persistent settings.
  • Dynamic Updates: Automatically refreshes views when preferences change.
  • Code Organization: Static keys keep the codebase clean and reusable.

Learn More​