What is the @State property wrapper?
Updated for Xcode 14.2
SwiftUI uses the @State property wrapper to allow us to modify values inside a struct, which would normally not be allowed because structs are value types.
When we put @State before a property, we effectively move its storage out from our struct and into shared storage managed by SwiftUI. This means SwiftUI can destroy and recreate our struct whenever needed (and this can happen a lot!), without losing the state it was storing.
@State should be used with simple struct types such as String, Int, and arrays, and generally shouldn’t be shared with other views. If you want to share values across views, you should probably use @ObservedObject or @EnvironmentObject instead – both of those will ensure that all views will be refreshed when the data changes.
To re-enforce the local nature of @State properties, Apple recommends you mark them as private, like this:
@State private var username = ""This isn’t required, but it seems like smart practice.
Tip: You can use @State to track reference types if you want, you just won’t be notified when they change. This is particularly helpful for classes that don’t conform to the ObservableObject protocol.
SAVE 50% To celebrate WWDC23, all our books and bundles are half price, so you can take your Swift knowledge further without spending big! Get the Swift Power Pack to build your iOS career faster, get the Swift Platform Pack to builds apps for macOS, watchOS, and beyond, or get the Swift Plus Pack to learn advanced design patterns, testing skills, and more.
Similar solutions…
- What is the @GestureState property wrapper?
- What is the @ObservedObject property wrapper?
- What is the @ScaledMetric property wrapper?
- What is the @AppStorage property wrapper?
- What is the @FocusState property wrapper?
