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詳解IOS串行隊列與并行隊列進(jìn)行同步或者異步的實例

更新時間：2017年07月28日 11:54:20 作者：aron1992

這篇文章主要介紹了詳解IOS串行隊列與并行隊列進(jìn)行同步或者異步的實例的相關(guān)資料,IOS中GCD的隊列分為串行隊列和并行隊列，任務(wù)分為同步任務(wù)和異步任務(wù)，他們的排列組合有四種情況這里就一一分析下，需要的朋友可以參考下

詳解IOS串行隊列與并行隊列進(jìn)行同步或者異步的實例

IOS中GCD的隊列分為串行隊列和并行隊列，任務(wù)分為同步任務(wù)和異步任務(wù)，他們的排列組合有四種情況，下面分析這四種情況的工作方式。

同步任務(wù)，使用GCD dispatch_sync 進(jìn)行派發(fā)任務(wù)

- (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);
    });
  }
}

結(jié)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方法是在主線程中調(diào)用的，結(jié)果看到使用的串行隊列和使用并行隊列看到的結(jié)果都是發(fā)生在當(dāng)前線程：主線程中，沒有開啟新的線程處理任務(wù)，任務(wù)的調(diào)度也是串行調(diào)度的。

異步任務(wù)，使用GCD dispatch_async 進(jìn)行派發(fā)任務(wù)

- (void)testAsync {
  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_async(serialQueue, ^{
      [NSThread sleepForTimeInterval:0.3];
      NSLog(@"==>%@ async serial XXX>%d", [NSThread currentThread], i);
    });
  }

  NSLog(@"====concurrentQueue====");
  for (int i = 0; i<10; i++) {
    dispatch_async(concurrentQueue, ^{
      [NSThread sleepForTimeInterval:0.3];
      NSLog(@"==>%@ async concurrent ====>%d", [NSThread currentThread], i*i);
    });
  }
}
`

結(jié)果如下：

2017-03-01 01:45:36.125 Demo ====serialQueue====
2017-03-01 01:45:36.125 Demo ====concurrentQueue====
2017-03-01 01:45:36.494 {number = 3, name = (null)} async concurrent ====>0
2017-03-01 01:45:36.494 {number = 5, name = (null)} async concurrent ====>4
2017-03-01 01:45:36.494 {number = 4, name = (null)} async concurrent ====>1
2017-03-01 01:45:36.494 {number = 6, name = (null)} async concurrent ====>16
2017-03-01 01:45:36.494 {number = 8, name = (null)} async serial XXX>0
2017-03-01 01:45:36.494 {number = 7, name = (null)} async concurrent ====>9
2017-03-01 01:45:36.494 {number = 9, name = (null)} async concurrent ====>25
2017-03-01 01:45:36.494 {number = 11, name = (null)} async concurrent ====>49
2017-03-01 01:45:36.494 {number = 10, name = (null)} async concurrent ====>36
2017-03-01 01:45:36.501 {number = 13, name = (null)} async concurrent ====>81
2017-03-01 01:45:36.501 {number = 12, name = (null)} async concurrent ====>64
2017-03-01 01:45:36.869 {number = 8, name = (null)} async serial XXX>1
2017-03-01 01:45:37.244 {number = 8, name = (null)} async serial XXX>2
2017-03-01 01:45:37.615 {number = 8, name = (null)} async serial XXX>3
2017-03-01 01:45:37.986 {number = 8, name = (null)} async serial XXX>4
2017-03-01 01:45:38.358 {number = 8, name = (null)} async serial XXX>5
2017-03-01 01:45:38.730 {number = 8, name = (null)} async serial XXX>6
2017-03-01 01:45:39.103 {number = 8, name = (null)} async serial XXX>7
2017-03-01 01:45:39.472 {number = 8, name = (null)} async serial XXX>8
2017-03-01 01:45:39.842 {number = 8, name = (null)} async serial XXX>9

testSync方法是在主線程中調(diào)用的，結(jié)果看到使用的串行隊列的異步任務(wù)會開啟一個子線程執(zhí)行任務(wù)，任務(wù)的調(diào)度是串行的
使用并行隊列的異步任務(wù)會開啟多個子線程并行的處理任務(wù)，任務(wù)的先后順序是不固定的，任務(wù)的調(diào)度方式是并行的

總結(jié)

同步任務(wù)：和使用的隊列無關(guān)，不會開啟子線程處理任務(wù)，會在當(dāng)前的線程中串行的調(diào)度任務(wù)，即一個任務(wù)完成之后繼續(xù)下一個任務(wù)，如果同步任務(wù)在主線程中調(diào)用，會阻塞主線程

異步任務(wù)：a. 使用串行隊列，會開啟一個子線程串行的調(diào)度任務(wù) b. 使用并行隊列，會開啟多個子線程并行的調(diào)度任務(wù)，這種情況用的是最多的。

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