SwiftUI AppStorage & SceneStorage

SwiftUI AppStorage & SceneStorage

For saving tiny pieces of data, such as a user's preference for Dark Mode or their high score in a game, Core Data and FileManager are overkill.

Historically, Apple developers used a tool called UserDefaults for this lightweight persistence.

SwiftUI wraps this functionality beautifully using two specialized property wrappers: @AppStorage and @SceneStorage.

The @AppStorage Wrapper

The @AppStorage property wrapper reads and writes values directly to UserDefaults.

When the value in UserDefaults changes, your SwiftUI view instantly re-renders!

You simply provide a unique string key, and a default value to use if the key hasn't been saved yet.

import SwiftUI

struct SettingsView: View {
    // Look for "isDarkMode" in UserDefaults, default to false
    @AppStorage("isDarkMode") private var isDarkMode = false
    var body: some View {
        VStack {
            Toggle("Enable Dark Mode", isOn: $isDarkMode)
                .padding()
            Text(isDarkMode ? "Dark Theme Active" : "Light Theme Active")
        }
    }
}

If the user quits the app and reopens it tomorrow, isDarkMode will perfectly remember its last state!

The @SceneStorage Wrapper

While @AppStorage saves data globally across the entire app permanently, @SceneStorage is slightly different.

@SceneStorage is used for State Restoration. It saves data specific to a single window (scene), and the data is destroyed if the user completely force-quits the app.

It is primarily used to remember what the user was currently typing or reading if iOS temporarily suspends the app in the background.

struct TextEditorView: View {
    // Remembers the text only while the app is alive/suspended
    @SceneStorage("draftText") private var draftText = ""
    var body: some View {
        TextEditor(text: $draftText)
            .padding()
    }
}

If you are on an iPad with multiple windows of the same app open, each window gets its own separate @SceneStorage draft!

When to use which?

• @AppStorage: Use for global user settings, high scores, login tokens, or permanent preferences.
• @SceneStorage: Use for temporary UI state, like remembering which tab is selected or the text in an unfinished draft.
• Core Data / Disk: Use for large amounts of complex, relational data.