Swift GCD

var queue: dispatch_queue_t = dispatch_get_main_queue()// 主线程

queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0)// 后台执行

// 异步执行队列任务

dispatch_async(queue, { () -> Void in

print("开新线程执行")

})

// 延时执行

var delta:Int64 = Int64(2 * NSEC_PER_SEC)// 2s后执行,可能不仅限于2s

delta = Int64(100 * NSEC_PER_MSEC)//100毫秒后执行

// NSEC_PER_MSEC

let when: dispatch_time_t = dispatch_time(DISPATCH_TIME_NOW, delta)

dispatch_after(when, queue) { () -> Void in

print("dispatch_after")

}

// 只执行一次

struct Static {

static var onceToken: dispatch_once_t = 0

static var value: String!

}

dispatch_once(&Static.onceToken, { () -> Void in

Static.value = "单例模式"

})

print("\(Static.value)")

dispatch_once(&Static.onceToken, { () -> Void in

Static.value = "改变值"

})

print("\(Static.value)")

// 分组执行

let group = dispatch_group_create()

queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)// 默认优先级执行

for (var i = 0; i<10; i++) {

//异步执行队列任务

dispatch_group_async(group, queue, { () -> Void in

Static.value = Static.value + "1"

print("\(Static.value)")

})

}

// 分组队列执行完毕后执行

dispatch_group_notify(group, queue) { () -> Void in

print("dispatch_group_notify")

}

// 串行队列：只有一个线程，加入到队列中的操作按添加顺序依次执行。

let serialQueue = dispatch_queue_create("yangj", DISPATCH_QUEUE_SERIAL)

for (var i = 0; i<10; i++) {

//异步执行队列任务

dispatch_async(serialQueue, { () -> Void in

//Static.value = Static.value + "1"

//println("\(Static.value)")

})

}

// 并发队列：有多个线程，操作进来之后它会将这些队列安排在可用的处理器上，同时保证先进来的任务优先处理。

let globalQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)

for (var i = 0; i<10; i++) {

//异步执行队列任务

dispatch_async(globalQueue, { () -> Void in

//Static.value = Static.value + "1"

//println("\(Static.value)")

})

}

}