NEW: Subscribe to Hacking with Swift+ and accelerate your learning! >>

What is the @State property wrapper?

Paul Hudson    @twostraws   

Updated for Xcode 12.0

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 and Int, 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.

Hacking with Swift is sponsored by NSSpain

SPONSORED Announcing NSSpain 2020: Remote Edition! An online, continuous conference for iOS developers. We’ll start on Thursday and finish on Friday, with talks, activities, and lots of fun for 36 hours, non-stop. Sound good? Join us!

Find out more

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: 5.0/5

Link copied to your pasteboard.