Swift Concurrency Task Cases

gistfile1.txt

Example 1:

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        task = Task {
            print("did start first url data request")
            _ = try await URLSession.shared.data(from: .init(string: "https://httpbin.org/delay/10")!)
            print("did finish first url data request")
            print("did start second url data request")
            _ = try await URLSession.shared.data(from: .init(string: "https://httpbin.org/delay/10")!)
            print("did finish second url data request")
        }
        Task {
            try await Task.sleep(for: .seconds(1))
            task?.cancel()
        }
    }
    
    Console Output:
    1. did start first url data request
    
Example 2:
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        task = Task {
            do {
                print("did start first url data request")
                _ = try await URLSession.shared.data(from: .init(string: "https://httpbin.org/delay/10")!)
                print("did finish first url data request")
                print("did start second url data request")
                _ = try await URLSession.shared.data(from: .init(string: "https://httpbin.org/delay/10")!)
                print("did finish second url data request")
            } catch {
                print(error)
            }
        }
        Task {
            try await Task.sleep(for: .seconds(1))
            task?.cancel()
        }
    }
    
    Colsole Output: 
    1. did start first url data request
    2. Error Domain=NSURLErrorDomain Code=-999 "cancelled" UserInfo={NSErrorFailingURLStringKey=https://httpbin.org/delay/10, NSErrorFailingURLKey=https://httpbin.org/delay/10, _NSURLErrorRelatedURLSessionTaskErrorKey=(
    "LocalDataTask <0E177C95-01EC-43E6-B4E8-68D80B5D6A64>.<1>"
), _NSURLErrorFailingURLSessionTaskErrorKey=LocalDataTask <0E177C95-01EC-43E6-B4E8-68D80B5D6A64>.<1>, NSLocalizedDescription=cancelled}

Example 3

    func doSomething() async throws {
        throw NSError(domain: "", code: 0)
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        task = Task {
            print("did start first doSomething")
            _ = try await doSomething()
            print("did finish first doSomething")
        }
    }
    
    Console Output:
    1. did start first doSomething

Example 4

    func doSomething() async throws {
        throw NSError(domain: "", code: 0)
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        task = Task {
            do {
                print("did start first doSomething")
                _ = try await doSomething()
                print("did finish first doSomething")
            } catch {
                print(error)
            }
            print("did execute last line")
        }
    }
    
    Console Output:
    1. did start first doSomething
    2. Error Domain= Code=0 "(null)"
    3. did execute last line
    
    Example 5:
    
    func doSomething() async throws {
        throw NSError(domain: "", code: 0)
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        task = Task {
            do {
                print("did start first doSomething")
                _ = try await doSomething()
                print("did finish first doSomething")
            }
            print("did start first doSomething")
        }
    }
    
    Console Output:
    1. did start first url data request
    
    Example 6:

    func doSomething() async throws {
        throw NSError(domain: "", code: 0)
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        task = Task {
            do {
                print("did start first doSomething")
                _ = try await doSomething()
                print("did finish first doSomething")
            } catch let error as MyError {
                print("did catch error of type MyError")
            }
            print("did finish do catch")
        }
    }
    
    Console Output:
    1. did start first doSomething
    
    final class pocEscapingTests: XCTestCase {

    func testDefault() {
        SnapshotTesting.diffTool = .ksdiff

        let controller = TotoViewController()
        /*
        controller.loadViewIfNeeded()
        controller.view.drawHierarchy(in: .init(origin: .zero, size: .init(width: 320, height: 450)), afterScreenUpdates: true)
        controller.viewDidLoad()
         */
        print("log: \(#function):\(#line)")
        _ = verifySnapshot(of: controller, as: .image, record: true)
        print("log: \(#function):\(#line)")
    }
}

class TotoViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        print("log: \(#function):\(#line)")
        let semaphore = DispatchSemaphore(value: 0)
        print("log: \(#function):\(#line)")
        let task = Task.detached {
            print("log: \(#function):\(#line)")
            let result = try await URLSession.shared.data(from: .init(string: "https://httpbin.org/delay/10")!)
            print("log: \(#function):\(#line)")
            semaphore.signal()  // Signal that the task is done
            print("log: \(#function):\(#line)")
        }
        print("log: \(#function):\(#line)")
        semaphore.wait()
        print("log: \(#function):\(#line)")
    }
}