2
的關係,我很困惑與DispatchQueue和DispatchSemaphore.Like下面的例子:[遊樂場] bettwen DispatchQueue和DispatchSemaphore
let semaphore : DispatchSemaphore = DispatchSemaphore(value:1)
for i in 1...40 {
DispatchQueue.global().async{
semaphore.wait()
NSLog("......1-%d",i)
semaphore.signal()
}
}
我認爲它應該打印1 ... 40,其實,它只能打印約25中,結果如下所示:
2016-11-18 19:05:38.786 MyPlayground[7436:495171] ......1-1
2016-11-18 19:05:38.787 MyPlayground[7436:495175] ......1-2
......
2016-11-18 19:05:38.797 MyPlayground[7436:495258] ......1-23
2016-11-18 19:05:38.797 MyPlayground[7436:495244] ......1-24
有誰知道原因嗎?
感謝