Nonisolated Init

nonisolated-init.swift

import Dispatch

let someDispatchQueue = DispatchQueue()

@MainActor
class Foo {
    nonisolated static let shared = Foo() 
    
    var mybar: Bar // I only need to get this from the main actor
    // In the real code there are many properties; that's why I'm not tagging
    // each one @MainActor on its own, but it should boil down to the same thing.
    
    nonisolated init() {
        mybar = getCachedBar() // Warning: Main actor-isolated property 'mybar' can not be mutated from a nonisolated context; this is an error in the Swift 6 language mode
    }
    
    nonisolated func updateBar() {
        someDispatchQueue.async {            
            let newBar = createNewBarOMGItTakesSoLong()
            DispatchQueue.main.async {
                self.mybar = newBar
            }
        }
    }
}

class Bar {
    var i = 0
} // Nonsendable

func createNewBarOMGItTakesSoLong() -> sending Bar {
    let bar = Bar()
    for i in 0..<1000 { bar.i += i }
    return bar
}

func getCachedBar() -> sending Bar {
    Bar()
}