swift - OperationQueue 停止操作一段时间

Question

我使用的是 swift 3.0.2。 Xcode 8.3.1

我尝试使用 isSuspended = true 属性，但它不会停止操作。

当我取消一个 operation1 时，所有其他依赖于 operation1 的操作立即开始。

我希望他们等到我告诉他们。

请帮帮我!

编辑1:

意味着它不会停止操作:

我有操作队列 oq 和三个操作:op1、op2、op3

oq.addOperation(op1)
op2.addDependency(op1)
oq.addOperation(op2)
op3.addDependency(op2)
oq.addOperation(op3)

所有三个操作都需要 10 秒才能执行。

添加第三个操作后，我设置了 isSuspended = true

My log:
op1 started
(-- set `isSuspended` to true)
(after 10 seconds)
op2 started
(after 10 seconds)
op3 started

当我将isSuspended设置为true时，我以为op1正在执行，没问题。但是为什么op2开始了？？？

这是我的 File.swift:

import Foundation

class PendingOps {
//    lazy var downloadInProgress = [Int: Operation]()
    // current tracklist

    var downloadQueue: OperationQueue {
        let queue = OperationQueue()
        queue.qualityOfService = .background
        queue.name = "Offline queue"
        queue.maxConcurrentOperationCount = 1
        return queue
    }
}


class op: Operation {
    var nam:String = ""

    init(nam: String) {
        self.nam = nam
    }

    override func main() {
        print("\(self.nam) started");

        sleep(10)

        print("\(self.nam) ended");
    }
}

这是 ViewController 的 viewDidLoad() 函数:

override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        let test = PendingOps()

        let o1 = op(nam: "o1")
        let o2 = op(nam: "o2")
        o2.addDependency(o1)
        let o3 = op(nam: "o3")
        o3.addDependency(o2)

        test.downloadQueue.addOperation(o1)

        test.downloadQueue.isSuspended = true        
        print(test.downloadQueue.isSuspended)

        test.downloadQueue.addOperation(o2)
        test.downloadQueue.addOperation(o3)

    }

Answer 1

您的计算属性 downloadQueue 在每次调用时创建一个独立队列。 IE。您正在暂停第一个创建的队列，但第二个和第三个队列不受影响。

要修复它，只创建队列一次，可能在 init()

中

class PendingOps {
    var downloadQueue: OperationQueue!

    init() {
        let queue = OperationQueue()
        queue.qualityOfService = .background
        queue.name = "Offline queue"
        queue.maxConcurrentOperationCount = 1
        downloadQueue = queue
    }
}

---

Playground 示例:

class PendingOps {
    var downloadQueue: OperationQueue!

    init() {
        let queue = OperationQueue()
        queue.qualityOfService = .background
        queue.name = "Offline queue"
        queue.maxConcurrentOperationCount = 1
        downloadQueue = queue
    }
}

class op: Operation {
    var nam:String = "?"

    init(nam: String) {
        self.nam = nam
    }

    override func main() {
        print("\(self.nam) started");

        sleep(1)

        print("\(self.nam) ended");
    }
}

func didLoad() {
    let test = PendingOps()

    let o1 = op(nam: "o1")
    let o2 = op(nam: "o2")
    o2.addDependency(o1)
    let o3 = op(nam: "o3")
    o3.addDependency(o2)

    test.downloadQueue.addOperation(o1)

    test.downloadQueue.isSuspended = true
    print(test.downloadQueue.isSuspended)

    test.downloadQueue.addOperation(o2)
    test.downloadQueue.addOperation(o3)

}

didLoad()

PlaygroundPage.current.needsIndefiniteExecution = true

打印:

o1 started
true
o1 ended