Some questions about async await threading in Swift's new concurrency model.

swift-async-await-example.swift

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        Task {
            // 1️⃣❓ UIViewController is in a MainActor context, so this Task
            // will inherit that, so the following pretend expensive call will
            // be on the main thread and likely block?
            ExpensiveOperationPerformer.doExpensiveLoopAndPrint()
        }

        Task.detached {
            // 2️⃣❓ Is this guaranteed to be off the main thread, so perhaps a
            // better way to do a one-off, expensive operation? If it's not
            // guaranteed, how would I ensure that? Wrap it in an actor 
            // instead of a class? What if it's not my class/I can't 
            // change the code?
            ExpensiveOperationPerformer.doExpensiveLoopAndPrint()
        }

        Task {
            ExpensiveOperationPerformer.printSomeNetworkData()
        }
    }
}

class ExpensiveOperationPerformer {
    @MainActor
    static func printSomeNetworkData() async throws {
        let url = URL(string: "https://example.com/example.json")!
        
        // 3️⃣❓ Will this time consuming network call be guaranteed to NOT
        // execute on main, despite the MainActor context? Or will it block?
        let (data, response) = try await URLSession.data(for: url)
        print(data)
    }

    static func doExpensiveLoopAndPrint() async {
        let upperEnd = 9_999_999_999
        var sum = 0

        for i in 0 ..< upperEnd {
            sum += 1
        }

        print(sum)
    }
}