1、組：dispatch_group
多個(gè)網(wǎng)絡(luò)請(qǐng)求執(zhí)行完，再執(zhí)行刷新

dispatch_group_t group = dispatch_group_create();
NSLog(@"開始執(zhí)行");

dispatch_group_enter(group);
dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
   NSLog(@"網(wǎng)絡(luò)請(qǐng)求1");
   dispatch_group_leave(group);
}) ;

dispatch_group_enter(group);
dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
   NSLog(@"網(wǎng)絡(luò)請(qǐng)求2");
   dispatch_group_leave(group);
}) ;

dispatch_group_enter(group);
dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
   NSLog(@"網(wǎng)絡(luò)請(qǐng)求3");
   dispatch_group_leave(group);
}) ;

dispatch_group_notify(group, dispatch_get_main_queue(), ^{
     NSLog(@"刷新界面");
 });
dispatch_group_wait(group, DISPATCH_TIME_FOREVER) ;
NSLog(@"等我一下");

以上代碼運(yùn)行打?。?/p>

開始執(zhí)行
網(wǎng)絡(luò)請(qǐng)求1
網(wǎng)絡(luò)請(qǐng)求2
網(wǎng)絡(luò)請(qǐng)求3
等我一下
刷新界面

2、dispatch_once 通常在創(chuàng)建單例時(shí)使用
3、dispatch_after 延遲執(zhí)行
4、dispatch_barrier_async 柵欄函數(shù)
分割異步任務(wù)

dispatch_group_t group = dispatch_group_create();
dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
   for (int i = 0; i< 3; i++) {
         NSLog(@"任務(wù)1");
    }
}) ;

dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
   for (int i = 0; i< 3; i++) {
         NSLog(@"任務(wù)2");
    }
}) ;

dispatch_barrier_async(dyConcurrent, ^{
        
        NSLog(@"攔一下");
    });

dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
   for (int i = 0; i< 3; i++) {
         NSLog(@"任務(wù)3");
    }
}) ;

dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
   for (int i = 0; i< 3; i++) {
         NSLog(@"任務(wù)4");
    }
}) ;

打印結(jié)果：121212攔一下343434

5、dispatch_apply 快速遍歷
6、信號(hào)量 dispatch_semaphore
可控制最大并發(fā)

dispatch_semaphore_t  cacheSemphore =  dispatch_semaphore_create(5);
for (int i = 0; i< 10; i++) {
     dispatch_async(dispatch_queue_create("dyConcurrent1", DISPATCH_QUEUE_CONCURRENT), {
         dispatch_semaphore_wait(cacheSemphore , DISPATCH_TIME_FOREVER);
         NSLog(@"任務(wù)%ld",(long)i);
         sleep(1);
         NSLog(@"到我了");
         dispatch_semaphore_signal(cacheSemphore);
     });
}

打印結(jié)果：

任務(wù)0
任務(wù)1
任務(wù)2
任務(wù)3
任務(wù)4
到我了
到我了
到我了
到我了
到我了
任務(wù)5
任務(wù)6
任務(wù)7
任務(wù)8
任務(wù)9
到我了
到我了
到我了
到我了
到我了