Nonisolated methods in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the nonisolated keyword mean in Swift concurrency?

It means the method can be called without switching to the actor's isolated context. The method runs without actor isolation, allowing safe access to non-isolated data.

intermediate

Why use nonisolated methods inside an actor?

To allow some methods to run without waiting for actor isolation, improving performance for read-only or stateless operations that don't need exclusive access.

intermediate

Can a nonisolated method access actor-isolated state directly?

No. Nonisolated methods cannot access actor-isolated properties or methods directly because they run outside the actor's isolation.

beginner

Example: How to declare a nonisolated method in an actor?

Inside an actor, write nonisolated func methodName() { ... } to mark the method as nonisolated.

beginner

What happens if you call a normal actor method from outside the actor?

The call is asynchronous and requires awaiting because the method runs in the actor's isolated context to ensure safe access.

What is the main purpose of marking a method as nonisolated in a Swift actor?

A To make the method asynchronous

B To prevent the method from being called

C To allow the method to run without actor isolation

D To make the method private

Nonisolated methods run outside the actor's isolation, allowing synchronous calls without awaiting.

Can a nonisolated method access actor-isolated properties directly?

A Yes, always

B Only if called from inside the actor

C Only if marked async

D No, never

Nonisolated methods cannot access actor-isolated state directly because they run outside the actor's isolation.

Which keyword do you use to mark a method as running outside actor isolation?

A nonisolated

B isolated

C async

D private

The nonisolated keyword marks methods that run outside actor isolation.

What happens when you call a normal actor method from outside the actor?

A It runs synchronously

B It requires awaiting because it runs asynchronously

C It throws an error

D It runs without isolation

Normal actor methods require awaiting because they run asynchronously inside the actor's isolated context.

Which of these is a good use case for a nonisolated method?

A Performing stateless calculations

B Reading actor-isolated properties

C Modifying actor state

D Calling other isolated methods

Nonisolated methods are good for stateless or read-only operations that don't need actor isolation.

Explain what a nonisolated method is in Swift actors and why you might use it.

Think about how actor isolation controls access and when you might want to bypass it safely.

Describe the difference between calling a normal actor method and a nonisolated method from outside the actor.

Consider how actor isolation affects method calls and concurrency.