operationdependencies

operationdependencies

class FirstPrintOperation: Operation {
    let stringToPrint: String
    init(stringToPrint: String = "I don't have manners") {
        self.stringToPrint = stringToPrint
        super.init()
    }
    override func main() {
        guard !isCancelled else { return }
        print(stringToPrint)
    }
}

class SecondPrintOperation: Operation {
    let stringToPrint: String
    init(stringToPrint: String = "This isn't \"Hello, World\"") {
        self.stringToPrint = stringToPrint
        super.init()
    }
    override func main() {
        guard !dependencies.contains(where: { $0.isCancelled }), !isCancelled else {
            return
        }
        print(stringToPrint)
    }}

let firstPrintOperation = FirstPrintOperation(stringToPrint: "FirstPrintOperation")
let secondPrintOperation = SecondPrintOperation(stringToPrint: "SecondPrintOperation")
secondPrintOperation.addDependency(firstPrintOperation)

let multipleOperationsQueue = OperationQueue()
multipleOperationsQueue.addOperations([firstPrintOperation, secondPrintOperation], waitUntilFinished: true)