Global Actors in Swift Concurrency


Steven Curtis
3 min readAug 28


Photo by Kyle Glenn on Unsplash

Introduced in Swift 5.5 along with Swift’s new concurrency model, global actors provide synchronization and ensure correct data access.

Let’s take a look.

Difficulty: Beginner | Easy | Normal | Challenging

This article has been developed using Xcode 14.2, and Swift 5.7.2


- Be able to produce a “Hello, World!” SwiftUI project

It might be nice if you had some knowledge of:

- Actors are a conceptual model used to deal with concurrency

- Be familiar with @MainActor

Keywords and Terminology

@MainActor: is a Swift attribute used to indicate that a type or function must be executed on the main thread.

Global Actors: Singleton actors which can be used to provide synchronization and ensure correct data access in concurrent contexts

Singleton: A way of instantiation that guarantees that only one instance of a class is created

Is a global actor the same as a main actor?

Not quite.

@MainActor is a predefined global actor in Swift and represents the main dispatch queue. @Mainactor is predefined, and represents the main dispatch queue. Because of this, @MainActor will usually be used for UI tasks that need to be run on the main queue.

We can create our own global actors.

struct CustomGlobalActor {
actor ActorType { }

static let shared: ActorType = ActorType()

class MyClass {
var uiProperty: String = "Hello, UI!"

var customProperty: String = "Hello, Custom!"

func updateUIProperty(value: String) {
uiProperty = value

func updateCustomProperty(value: String) {
customProperty = value

let myClass = MyClass()
await print(myClass.customProperty)

Why Use Global Actor?

Shared Resources