FREE TRIAL: Accelerate your app development career with Hacking with Swift+! >>

What is the @AppStorage property wrapper?

Paul Hudson    @twostraws   

Updated for Xcode 13.0

New in iOS 14

SwiftUI has a dedicated property wrapper for reading values from UserDefaults, which will automatically reinvoke your view’s body property when the value changes. That is, this wrapper effectively watches a key in UserDefaults, and will refresh your UI if that key changes.

For example, this will watch UserDefaults for a “username” key, which will be set when the button is pressed:

struct ContentView: View {
    @AppStorage("username") var username: String = "Anonymous"

    var body: some View {
        VStack {
            Text("Welcome, \(username)!")

            Button("Log in") {
                username = "@twostraws"
            }
        }
    }
}

Changing username above will cause the new string to be written to UserDefaults immediately, while also updating the view. The same would be true if we had used the older method:

UserDefaults.standard.set("@twostraws", forKey: "username")`

@AppStorage will watch UserDefaults.standard by default, but you can also make it watch a particular app group if you prefer, like this:

@AppStorage("username", store: UserDefaults(suiteName: "group.com.hackingwithswift.unwrap")) var username: String = "Anonymous"

Important: @AppStorage writes your data to UserDefaults, which is not secure storage. As a result, you should not save any personal data using @AppStorage, because it’s relatively easy to extract.

Hacking with Swift is sponsored by Sentry

SPONSORED With Sentry’s error and performance monitoring for iOS you see mobile vitals that actually matter, can solve any latency issues quickly, and learn how each release is performing over time.

Get started

Sponsor Hacking with Swift and reach the world's largest Swift community!

Similar solutions…

BUY OUR BOOKS
Buy Pro Swift Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift (Vapor Edition) Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Server-Side Swift (Kitura Edition) Buy Beyond Code

Was this page useful? Let us know!

Average rating: 4.2/5

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.