Example 2

import Foundation
import XCTest


class DelayedOperation: Operation {

    private var delay: TimeInterval

    init(_ delay: TimeInterval = 0) {
        self.delay = delay
    }

    override var isExecuting : Bool {
        get { return _executing }
        set {
            willChangeValue(forKey: "isExecuting")
            _executing = newValue
            didChangeValue(forKey: "isExecuting")
        }
    }
    private var _executing : Bool = false

    override var isFinished : Bool {
        get { return _finished }
        set {
            willChangeValue(forKey: "isFinished")
            _finished = newValue
            didChangeValue(forKey: "isFinished")
        }
    }
    private var _finished : Bool = false

    override func start() {

        guard delay > 0 else {
            _start()
            return
        }

        let deadline = DispatchTime.now() + delay
        DispatchQueue(label: "").asyncAfter(deadline: deadline) {
            self._start()
        }
    }

    private func _start() {

        guard !self.isCancelled else {
            print("\(self): operation is canceled")
            self.isFinished = true
            return
        }

        self.isExecuting = true
        self.main()
        self.isExecuting = false
        self.isFinished = true
    }
}

class WindowOperation: DelayedOperation {

    override func main() {
        print("\(self): Windows are closed via HomeKit.")
    }

    override var description: String { return "WindowOperation" }
}

class DoorOperation: DelayedOperation {

    override func main() {
        print("\(self): Doors are closed via HomeKit.")
    }

    override var description: String { return "DoorOperation" }
}

class TaxiOperation: DelayedOperation {

    override func main() {
        print("\(self): Taxi is ordered via Uber")
    }

    override var description: String { return "TaxiOperation" }
}



class CommandRealWorld: XCTestCase {

    func testCommandRealWorld() {
        prepareTestEnvironment {

            let siri = SiriShortcuts.shared

            print("User: Hey Siri, I am leaving my home")
            siri.perform(.leaveHome)

            print("User: Hey Siri, I am leaving my work in 3 minutes")
            siri.perform(.leaveWork, delay: 3) /// for simplicity, we use seconds

            print("User: Hey Siri, I am still working")
            siri.cancel(.leaveWork)
        }
    }
}

extension CommandRealWorld {

    struct ExecutionTime {
        static let max: TimeInterval = 5
        static let waiting: TimeInterval = 4
    }

    func prepareTestEnvironment(_ execution: () -> ()) {

        /// This method tells Xcode to wait for async operations. Otherwise the
        /// main test is done immediately.

        let expectation = self.expectation(description: "Expectation for async operations")

        let deadline = DispatchTime.now() + ExecutionTime.waiting
        DispatchQueue.main.asyncAfter(deadline: deadline) { expectation.fulfill() }

        execution()

        wait(for: [expectation], timeout: ExecutionTime.max)
    }
}

class SiriShortcuts {

    static let shared = SiriShortcuts()
    private lazy var queue = OperationQueue()

    private init() {}

    enum Action: String {
        case leaveHome
        case leaveWork
    }

    func perform(_ action: Action, delay: TimeInterval = 0) {
        print("Siri: performing \(action)-action\n")
        switch action {
        case .leaveHome:
            add(operation: WindowOperation(delay))
            add(operation: DoorOperation(delay))
        case .leaveWork:
            add(operation: TaxiOperation(delay))
        }
    }

    func cancel(_ action: Action) {
        print("Siri: canceling \(action)-action\n")
        switch action {
        case .leaveHome:
            cancelOperation(with: WindowOperation.self)
            cancelOperation(with: DoorOperation.self)
        case .leaveWork:
            cancelOperation(with: TaxiOperation.self)
        }
    }

    private func cancelOperation(with operationType: Operation.Type) {
        queue.operations.filter { operation in
            return type(of: operation) == operationType
        }.forEach({ $0.cancel() })
    }

    private func add(operation: Operation) {
        queue.addOperation(operation)
    }
}

User: Hey Siri, I am leaving my home
Siri: performing leaveHome-action

User: Hey Siri, I am leaving my work in 3 minutes
Siri: performing leaveWork-action

User: Hey Siri, I am still working
Siri: canceling leaveWork-action

DoorOperation: Doors are closed via HomeKit.
WindowOperation: Windows are closed via HomeKit.
TaxiOperation: operation is canceled