//dispatch_barrier_async使用在并行環(huán)境下，
//dispatch_barrier_async添加的任務會在之前的block全部運行完畢之后，才會繼續(xù)執(zhí)行，保證線程安全保證對非線程安全的對象進行正確的操作。
//運行完dispatch_barrier_async才會執(zhí)行后面的任務
//dispatch_barrier_async所在的線程跟前一個任務是同一線程

//延遲執(zhí)行
dispatch_after(dispatch_time(DISPATCH_TIME_NOW,(int64_t)(5*NSEC_PER_SEC)),dispatch_get_main_queue,dispatch_get_main_queue(),^{
NSLog(@"選擇性隊列延遲5秒執(zhí)行");
})
//自定義并行隊列
dispatch_queue_t queue=dispatch_queue_create("duoduo",DISPATCH_QUEUE_CONCURRENT);
dispatch_async(queue,^{
NSLog(@"dispatch_async-1-%@",[NSThread currentThread]);
});
dispatch_async(queue,^{
NSLog(@"dispatch_async-2-%@",[NSTread currentThread]);
});
dispatch_barrier_async(queue,^{
NSLog(@"dispatch_barrier_async-%@",[NSTread currentThread]);
});
dispatch_async(queue,^{
NSLog(@"dispatch_async-3-%@",[NSThread currentThread]);
});
dispatch_async(queue,^{
NSLog(@"dispatch_async-4-%@",[NSThread currentThread]);
});

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