January 2020
Intermediate to advanced
356 pages
6h 4m
Chinese
Content preview from Swift游戏开发经典实例
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32
｜
第
1
章
OperationQueue.main.addOperation {
//
当后台任务执行完，返回主队列刷新
UI
}
}
一个任务队列可以同时执行多个任务。它能够并行处理的任务数取决于几个因素，
如处理器的内核数以及任务的优先级。
默认情况下，任务队列所能并行处理的任务数由它自己决定。但是，通过设置
maxConcurrentOperationCount
属性，我们可以指定队列的并行操作数的最大值。
1.14
延迟执行
问题
我们可以在当前时间若干秒后再运行这段代码。
解决方案
使用
DispatchQueue
类的
asyncAfter
函数，我们可以让闭包推迟到未来某个时间
执行：
//
放一个炸弹，让它在
10
秒后爆炸
PlaceBomb()
let deadline = DispatchTime.now() + 10
DispatchQueue.main.asyncAfter(deadline: deadline, execute: {
//
时间到，嘣！
ExplodeBomb()
})
讨论
OperationQueue
实际上是基于
C
的
GCD API
的一个更高级的封装。使用
GCD
（
Grand
Central Dispatch
）执行的任务，基本上都是在“
Dispatch Queue
”中执行的，后者
几乎就和
OperationQueue
一模一样。在
GCD
中，我们可以向
Dispatch Queue
提交
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.