When to use actors

Actors in Swift are used to manage shared mutable state in a concurrent environment safely. They are similar to classes but provide automatic protection by serializing access to their state, ensuring that only one task can execute at a time on an actor. This helps prevent data races and makes concurrent programming more manageable.

Here are some specific scenarios where you might use actors:

Encapsulating Shared Mutable State: When you have a piece of state that is accessed and modified by multiple tasks, using an actor can help ensure that these accesses are serialized, preventing data races. For example, in the session A Swift Tour: Explore Swift’s features and design, the userstore is made an actor to synchronize concurrent accesses.
Main Actor for UI Updates: When dealing with UI updates, you often need to ensure that these updates happen on the main thread. Swift provides the main actor for this purpose. For instance, in the session Migrate your app to Swift 6, the main actor is used to guarantee that certain methods are called on the main thread.
Background Operations: When performing background operations that need to communicate with the main thread or other actors, you can use dedicated actors for these tasks. This is discussed in the session Migrate your app to Swift 6, where background operations are performed on dedicated actors, and they communicate using thread-safe value types.
Preventing Data Races: Actors help in preventing data races by ensuring that shared mutable state is not accessed simultaneously by multiple tasks. This is highlighted in the session Migrate your app to Swift 6, where the benefits of Swift 6's full enforcement of data isolation are discussed.

In summary, actors are a powerful feature in Swift for managing concurrency and ensuring data safety in your applications. They are particularly useful for encapsulating shared mutable state, ensuring UI updates happen on the main thread, performing background operations, and preventing data races.