1. Core Idea

@AppStorage is used to store persistent state that is backed by UserDefaults.

It behaves like @State, but the value:

• persists across app launches
• is shared across the app via a key

@AppStorage = @State + persistence (UserDefaults)

2. Definition

@AppStorage is a property wrapper that:

• reads from UserDefaults
• writes to UserDefaults
• updates the UI when the value changes

3. Basic Usage

@AppStorage("isDarkMode") var isDarkMode = false

• "isDarkMode" → key in UserDefaults
• false → default value

4. Example

struct SettingsView: View {

    @AppStorage("isDarkMode") var isDarkMode = false

    var body: some View {
        Toggle("Dark Mode", isOn: $isDarkMode)
    }
}