SwiftUI: What is @AppStorage property wrapper

Question

I used to save important App data like login credentials into UserDefaults using the following statement:

UserDefaults.standard.set("sample@email.com&quo         


        

Answer 1

@AppStorage is a convenient way to save and read variables from UserDefaults and use them in the same way as @State properties. It can be seen as a @State property which is automatically saved to (and read from) UserDefaults.

You can think of the following:

@AppStorage("emailAddress") var emailAddress: String = "sample@email.com"

as an equivalent of this (which is not allowed in SwiftUI and will not compile):

@State var emailAddress: String = "sample@email.com" {
    get {
        UserDefaults.standard.string(forKey: "emailAddress")
    }
    set {
        UserDefaults.standard.set(newValue, forKey: "emailAddress")
    }
}

Note that @AppStorage behaves like a @State: a change to its value will invalidate and redraw a View.

By default @AppStorage will use UserDefaults.standard. However, you can specify your own UserDefaults store:

@AppStorage("emailAddress", store: UserDefaults(...)) ...

Useful links:

• What is the @AppStorage property wrapper?
• AppStorage Property Wrapper SwiftUI