iOS开发之用GCD实现多线程

//因为是异步，所以开通了子线程，但是因为是串行队列，所以只需要开通1个子线程，它们在子线程中顺序执行。最常用。
dispatch_queue_t q1 = dispatch_queue_create("qqqqq", DISPATCH_QUEUE_SERIAL);
for (int i = 0; i < 10; i++) {
   dispatch_async(q1, ^{
       NSLog(@"11111%@",[NSThread currentThread]);
   });
}
//因为是异步，所以开通了子线程，且因为是并行队列，所以开通了好多个子线程，具体几个，无人知晓，看运气。线程数量无法控制，且浪费。
dispatch_queue_t q2 = dispatch_queue_create("wwwww", DISPATCH_QUEUE_CONCURRENT);
for (int i = 0; i < 10; i++) {
   dispatch_async(q2, ^{
       NSLog(@"22222%@",[NSThread currentThread]);
   });
}
//因为是同步，所以无论是并行队列还是串行队列，都是在主线程中执行
dispatch_queue_t q3 = dispatch_queue_create("eeeee", DISPATCH_QUEUE_SERIAL);
for (int i = 0; i < 10; i++) {
   dispatch_sync(q3, ^{
       NSLog(@"33333%@",[NSThread currentThread]);
   });
}
//全局队列和并行队列类似（全局队列不需要创建直接get即可，而导致其没有名字，不利于后续调试）
dispatch_queue_t q4 = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
for (int i = 0; i < 10; i++) {
   dispatch_sync(q4, ^{
       NSLog(@"44444%@",[NSThread currentThread]);
   });
}
for (int i = 0; i < 10; i++) {
   dispatch_async(q4, ^{
       NSLog(@"55555%@",[NSThread currentThread]);
   });
}

打印结果

2016-06-30 23:10:54.486 multithreaded[10087:519523] 22222<NSThread: 0x7f9a7ccd5470>{number = 5, name = (null)}

2016-06-30 23:10:54.486 multithreaded[10087:519524] 22222<NSThread: 0x7f9a7cf1a250>{number = 6, name = (null)}

2016-06-30 23:10:54.486 multithreaded[10087:519432] 33333<NSThread: 0x7f9a7ce044b0>{number = 1, name = main}

2016-06-30 23:10:54.486 multithreaded[10087:519517] 11111<NSThread: 0x7f9a7cc13150>{number = 2, name = (null)}

2016-06-30 23:10:54.486 multithreaded[10087:519525] 22222<NSThread: 0x7f9a7cf3d720>{number = 7, name = (null)}

2016-06-30 23:10:54.486 multithreaded[10087:519518] 22222<NSThread: 0x7f9a7ce151a0>{number = 3, name = (null)}

2016-06-30 23:10:54.486 multithreaded[10087:519522] 22222<NSThread: 0x7f9a7cd1cf20>{number = 4, name = (null)}

2016-06-30 23:10:54.487 multithreaded[10087:519526] 22222<NSThread: 0x7f9a7ccd8e80>{number = 8, name = (null)}

2016-06-30 23:10:54.487 multithreaded[10087:519523] 22222<NSThread: 0x7f9a7ccd5470>{number = 5, name = (null)}

2016-06-30 23:10:54.487 multithreaded[10087:519524] 22222<NSThread: 0x7f9a7cf1a250>{number = 6, name = (null)}

2016-06-30 23:10:54.487 multithreaded[10087:519432] 33333<NSThread: 0x7f9a7ce044b0>{number = 1, name = main}

2016-06-30 23:10:54.487 multithreaded[10087:519517] 11111<NSThread: 0x7f9a7cc13150>{number = 2, name = (null)}

2016-06-30 23:10:54.488 multithreaded[10087:519527] 22222<NSThread: 0x7f9a7ce0d8e0>{number = 9, name = (null)}

2016-06-30 23:10:54.488 multithreaded[10087:519525] 22222<NSThread: 0x7f9a7cf3d720>{number = 7, name = (null)}

2016-06-30 23:10:54.489 multithreaded[10087:519432] 33333<NSThread: 0x7f9a7ce044b0>{number = 1, name = main}

2016-06-30 23:10:54.489 multithreaded[10087:519517] 11111<NSThread: 0x7f9a7cc13150>{number = 2, name = (null)}