详解IOS串行队列与并行队列进行同步或者异步的实例
IOS中GCD的队列分为串行队列和并行队列，任务分为同步任务和异步任务，他们的排列组合有四种情况，下面分析这四种情况的工作方式。
同步任务，使用GCD dispatch_sync 进行派发任务
- (void)testSync {
dispatch_queue_t serialQueue = dispatch_queue_create("com.zyt.queue", DISPATCH_QUEUE_SERIAL);
dispatch_queue_t concurrentQueue = dispatch_queue_create("com.zyt.queue", DISPATCH_QUEUE_CONCURRENT);
NSLog(@"====serialQueue====");
for (int i = 0; i<10; i++) {
dispatch_sync(serialQueue, ^{
[NSThread sleepForTimeInterval:0.3];
NSLog(@"==>%@ sync serial XXX>%d", [NSThread currentThread], i);
});
}
NSLog(@"====concurrentQueue====");
for (int i = 0; i<10; i++) {
dispatch_sync(concurrentQueue, ^{
[NSThread sleepForTimeInterval:0.3];
NSLog(@"==>%@ sync concurrent ====>%d", [NSThread currentThread], i*i);
});
}
}
结果如下：
2017-03-01 01:36:22.835 Demo ====serialQueue====
2017-03-01 01:36:23.207 {number = 1, name = main} sync serial XXX>0
2017-03-01 01:36:23.578 {number = 1, name = main} sync serial XXX>1
2017-03-01 01:36:23.952 {number = 1, name = main} sync serial XXX>2
2017-03-01 01:36:24.325 {number = 1, name = main} sync serial XXX>3
2017-03-01 01:36:24.699 {number = 1, name = main} sync serial XXX>4
2017-03-01 01:36:25.072 {number = 1, name = main} sync serial XXX>5
2017-03-01 01:36:25.446 {number = 1, name = main} sync serial XXX>6
2017-03-01 01:36:25.746 {number = 1, name = main} sync serial XXX>7
2017-03-01 01:36:26.122 {number = 1, name = main} sync serial XXX>8
2017-03-01 01:36:26.489 {number = 1, name = main} sync serial XXX>9
2017-03-01 01:36:26.489 Demo ====concurrentQueue====
2017-03-01 01:36:26.864 {number = 1, name = main} sync concurrent ====>0
2017-03-01 01:36:27.236 {number = 1, name = main} sync concurrent ====>1
2017-03-01 01:36:27.611 {number = 1, name = main} sync concurrent ====>4
2017-03-01 01:36:27.985 {number = 1, name = main} sync concurrent ====>9
2017-03-01 01:36:28.354 {number = 1, name = main} sync concurrent ====>16
2017-03-01 01:36:28.726 {number = 1, name = main} sync concurrent ====>25
2017-03-01 01:36:29.100 {number = 1, name = main} sync concurrent ====>36
2017-03-01 01:36:29.474 {number = 1, name = main} sync concurrent ====>49
2017-03-01 01:36:29.849 {number = 1, name = main} sync concurrent ====>64
2017-03-01 01:36:30.223 {number = 1, name = main} sync concurrent ====>81
testSync方法是在主线程中调用的，结果看到使用的串行队列和使用并行队列看到的结果都是发生在当前线程：主线程中，没有开启新的线程处理任务，任务的调度也是串行调度的。
异步任务，使用GCD dispatch_async 进行派发任务
