Question

我尝试在Swift Playground中测试取消DispatchWork项目，虽然在执行的前几毫秒内出现了错误，我不确定它实际上指示了什么，我也无法判断错误是否导致取消而不是cancel()方法......

func testDispatchWorkItems() {
    let queue = DispatchQueue.global(qos: .userInitiated)
    var item: DispatchWorkItem?

    // create work item

    item = DispatchWorkItem {
        for i in 0 ... 100000 {
            if item!.isCancelled { break }
            print(i)
        }
    }

    // start it

    queue.async(execute: item!)

    // after three seconds, stop it

    queue.asyncAfter(deadline: .now() + 3) {
        item?.cancel()
    }
}

testDispatchWorkItems()

 2016-10-26 11:14:33.898
 com.apple.dt.Xcode.PlaygroundStub-macosx[30685:18567692] Error
 encountered communicating with Xcode: Error
 Domain=DVTPlaygroundCommunicationErrorDomain Code=1 "Cannot send data
 because stream is closed." UserInfo={NSLocalizedDescription=Cannot
 send data because stream is closed.}

有人知道这个错误表明了什么吗？

Answer 1

将needsIndefiniteExecution设置为true可以省略此警告。一旦操场执行比线程处理更早结束，就会发出警告。

import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true

Xcode：错误域= DVTPlaygroundCommunicationErrorDomain代码= 1

1 个答案: