NEW: Start my new Ultimate Portfolio App course with a free Hacking with Swift+ trial! >>

What is the @AppStorage property wrapper?

Paul Hudson    @twostraws   

Updated for Xcode 12.0

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") {
                self.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"
Hacking with Swift is sponsored by Fernando Olivares

SPONSORED Would you describe yourself as knowledgeable, but struggling when you have to come up with your own code? Fernando Olivares has a new book containing iOS rules you can immediately apply to your coding habits to see dramatic improvements, while also teaching applied programming fundamentals seen in refactored code from published apps.

Try the book!

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: 4.5/5

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.