如何取消后台运行的线程？（iOS）

这是我使用调度队列的函数，我想在后台运行时取消它。我该怎么做

 extension DispatchQueue {
    static func background(delay: Double = 0.0, background: (()->Void)? = nil, completion: (() -> Void)? = nil) {
        DispatchQueue.global(qos: .background).async {
            background?()
            if let completion = completion {
                DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: {
                    completion()
                })
            }
        }
    }       
 }

 DispatchQueue.background(background: {
        do {
        }
        catch let error {
            // Error handling
        }
    }, completion:{
 })

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您一定要查看有关以下内容的苹果官方文档：

还有这个

---

希望它能帮助您建立关于iOS和更高级别API的知识库。

您一定要查看有关以下内容的苹果官方文档：

还有这个

---

希望它能帮助您建立有关iOS和更高级别API的知识库。

您可以与DispatchGroup一起使用DispatchWorkItem

    // create a work item with the custom code
    let workItem = DispatchWorkItem {
          // Insert your code here
    }


   //Create dispatch group
    let dispatchGroup = DispatchGroup()

   // execute the workItem with dispatchGroup
    DispatchQueue.global().async(group: dispatchGroup, execute: workItem)

   //Handle code after the completion of global queue
    dispatchGroup.notify(queue: DispatchQueue.global()) {
            print("global queue execution completed")
        }

   //when the App goes to background cancel the workItem
     workItem.cancel()

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您可以将DispatchWorkItem与DispatchGroup一起使用

    // create a work item with the custom code
    let workItem = DispatchWorkItem {
          // Insert your code here
    }


   //Create dispatch group
    let dispatchGroup = DispatchGroup()

   // execute the workItem with dispatchGroup
    DispatchQueue.global().async(group: dispatchGroup, execute: workItem)

   //Handle code after the completion of global queue
    dispatchGroup.notify(queue: DispatchQueue.global()) {
            print("global queue execution completed")
        }

   //when the App goes to background cancel the workItem
     workItem.cancel()

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如果要取消后台线程，请使用nsoperationqueue而不是GCDi如果要取消后台线程，请使用nsoperationqueue而不是GCDh如何将此调度队列转换为操作队列？如何将此调度队列转换为操作队列？我喜欢您的回答，但如何知道DispatchQueue.global（qos:.background）.async（execute:workItem！）在进入DispatchQueue.main.async（execute:workItem）？我喜欢你的答案，但我怎么知道DispatchQueue.global（qos:.background）.async（execute:workItem！）在进入DispatchQueue.main.async（execute:workItem！）之前已经完成了执行？