Hi everyone 👋

After my mTLS post, I wanted to write up what I've learned about actors and the concurrency model in Swift 6: how they work, the mistakes I made along the way, and what changed in Swift 6.2. Corrections are very welcome!

1. What an actor gives you

An actor is a reference type that protects its own mutable state. Only one task runs on an actor at a time, so the compiler can prove there are no data races. Code outside the actor has to await to reach that state.

enum BankError : Error { case insufficientFunds }

actor BankAccount { private ( set ) var balance : Decimal = 0

func deposit ( _ amount : Decimal ) { balance += amount }

func withdraw ( _ amount : Decimal ) throws { guard balance >= amount else { throw BankError . insufficientFunds } balance -= amount } }

let account = BankAccount ( ) await account . deposit ( 100 ) let current = await account . balance

Enter fullscreen mode

Exit fullscreen mode

Inside the actor, calls are synchronous.…