创建可以取消的子线程任务
typealias Task = (_ cancel : Bool) -> Void
func delay(_ time: TimeInterval, task: @escaping ()->()) -> Task? {
func dispatch_later(_ block: @escaping ()->()) {
let t = DispatchTime.now() + time
DispatchQueue.main.asyncAfter(deadline: t, execute: block)
}
var closure: (()->Void)? = task
var result: Task?
let delayedClosure: Task = {
cancel in
if let internalClosure = closure {
if (cancel == false) {
DispatchQueue.main.async(execute: internalClosure)
}
}
closure = nil
result = nil
}
result = delayedClosure
dispatch_later {
if let delayedClosure = result {
delayedClosure(false)
}
}
return result;
}
func cancel(_ task: Task?) {
task?(true)
}
delay(2) { print("2 秒后输出") }
let task = delay(5) { print("拨打 110") }
// 仔细想一想..
// 还是取消为妙..
cancel(task)
一般的应用子线程任务主线程刷新
// 创建目标队列
let workingQueue = DispatchQueue(label: "my_queue")
// 派发到刚创建的队列中，GCD 会负责进行线程调度
workingQueue.async {
// 在 workingQueue 中异步进行
print("努力工作")
Thread.sleep(forTimeInterval: 2) // 模拟两秒的执行时间
DispatchQueue.main.async {
// 返回到主线程更新 UI
print("结束工作，更新 UI")
}
}
