基礎(chǔ)使用
//使用方法,先創(chuàng)建隊列,在創(chuàng)建任務(wù)
// 串行隊列的創(chuàng)建方法
dispatch_queue_t queue= dispatch_queue_create("test.queue", DISPATCH_QUEUE_SERIAL);
// 并發(fā)隊列的創(chuàng)建方法
dispatch_queue_t queue= dispatch_queue_create("test.queue", DISPATCH_QUEUE_CONCURRENT);
// 同步執(zhí)行任務(wù)創(chuàng)建方法
dispatch_sync(queue, ^{
NSLog(@"%@",[NSThread currentThread]); // 這里放任務(wù)代碼
});
// 異步執(zhí)行任務(wù)創(chuàng)建方法
dispatch_async(queue, ^{
NSLog(@"%@",[NSThread currentThread]); // 這里放任務(wù)代碼
});
GCD的延時執(zhí)行方法 dispatch_after
//當(dāng)我們需要延遲執(zhí)行一段代碼時轴咱，就需要用到GCD的dispatch_after方法
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
// 2秒后異步執(zhí)行這里的代碼...
NSLog(@"run-----");
});
GCD的一次性代碼(只執(zhí)行一次) dispatch_once
//我們在創(chuàng)建單例、或者有整個程序運行過程中只執(zhí)行一次的代碼時，我們就用到了GCD的dispatch_once方法。使用dispatch_once函數(shù)能保證某段代碼在程序運行過程中只被執(zhí)行1次
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
// 只執(zhí)行1次的代碼(這里面默認是線程安全的)
});
柵欄操作
- (void)barrier
{
dispatch_queue_t queue = dispatch_queue_create("12312312", DISPATCH_QUEUE_CONCURRENT);
dispatch_async(queue, ^{
NSLog(@"----1-----%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"----2-----%@", [NSThread currentThread]);
});
dispatch_barrier_async(queue, ^{
NSLog(@"----barrier-----%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"----3-----%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"----4-----%@", [NSThread currentThread]);
});
}
//輸出結(jié)果(先執(zhí)行barrier前的再執(zhí)行barrier,之后再執(zhí)行barrier后的)
// --1--
//--2--
//barrier
//--3--
//--4--
GCD線程之間的通訊
//在線程中進行耗時操作拿到數(shù)據(jù)后返回主線程進行reload
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
for (int i = 0; i < 2; ++i) {
NSLog(@"1------%@",[NSThread currentThread]);
}
// 回到主線程
dispatch_async(dispatch_get_main_queue(), ^{
NSLog(@"2-------%@",[NSThread currentThread]);
});
});
ios 監(jiān)視下載全部完成-GCD隊列
dispatch_group_t group = dispatch_group_create();
for (int i=0; i<10; i++) {
dispatch_group_enter(group);
//dispatch_sync(dispatch_get_global_queue(0, 0), ^{
dispatch_async(dispatch_get_global_queue(0, 0), ^{
sleep(2);
NSLog(@"任務(wù) %d 完成",i);
dispatch_group_leave(group);
});
}
dispatch_group_notify(group, dispatch_get_global_queue(0, 0), ^{
NSLog(@"任務(wù)完成");
});
//--------------------------------------------------------------------------
dispatch_group_t group = dispatch_group_create();
dispatch_group_enter(group);
dispatch_async(dispatch_get_global_queue(0, 0), ^{
sleep(5);
NSLog(@"任務(wù)一完成");
dispatch_group_leave(group);
});
dispatch_group_enter(group);
dispatch_async(dispatch_get_global_queue(0, 0), ^{
sleep(8);
NSLog(@"任務(wù)二完成");
dispatch_group_leave(group);
});
dispatch_group_notify(group, dispatch_get_global_queue(0, 0), ^{
NSLog(@"任務(wù)完成");
});
//如何用GCD同步若干個異步調(diào)用赏僧？
// 創(chuàng)建隊列組
dispatch_group_t group = dispatch_group_create();
// 獲取全局并發(fā)隊列
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_group_async(group, queue, ^{ /*任務(wù)1 */ });
dispatch_group_async(group, queue, ^{ /*任務(wù)2 */ });
dispatch_group_async(group, queue, ^{ /*任務(wù)3 */ });
// 當(dāng)并發(fā)隊列組中的任務(wù)執(zhí)行完畢后才會執(zhí)行這里的代碼
dispatch_group_notify(group, dispatch_get_main_queue(), ^{
// 合并任務(wù)結(jié)果
});
