GCD-継続学習中

インタフェースでデータを取得した後、データ量が小さい場合はメインスレッドで処理したほうがいいですが、データ量が大きくなるとスレッドで処理する必要があります.そうしないと、使用時に明らかなカートン現象が感じられます.

IOS：マルチスレッド処理方法

1.NSThread 2.NSOperation 3.GCD

今日はGCDを勉強します

1.dispatch_の作成queue_t理解順序実行と同時実行

//serial queue     FIFO DISPATCH_QUEUE_SERIAL
//concurrent queue      DISPATCH_QUEUE_CONCURRENT

コード:パラメータはDISPATCH_QUEUE_CONCURRENT

NSDate *date = [NSDate date];
NSString *dateString = [date description];
const char *queuename = [dateString UTF8String];
dispatch_queue_t myqueue = dispatch_queue_create(queuename, DISPATCH_QUEUE_CONCURRENT);
dispatch_async(myqueue, ^{
    [self downloadTime:6];
});
dispatch_async(myqueue, ^{
    [self downloadTime:3];
});
dispatch_async(myqueue, ^{
    [self downloadTime:2];
});

実行結果:

2002016-06-22 17:21:13.613 Learn-IOS[24089:546819]  2 
2016-06-22 17:21:14.610 Learn-IOS[24089:546712]  3 
2016-06-22 17:21:17.609 Learn-IOS[24089:546718]  6 

コード:パラメータはDISPATCH_QUEUE_SERIAL

NSDate *date = [NSDate date];
NSString *dateString = [date description];
const char *queuename = [dateString UTF8String];
dispatch_queue_t myqueue = dispatch_queue_create(queuename, DISPATCH_QUEUE_SERIAL);
dispatch_async(myqueue, ^{
    [self downloadTime:6];
});
dispatch_async(myqueue, ^{
    [self downloadTime:3];
});
dispatch_async(myqueue, ^{
    [self downloadTime:2];
});

実行結果:

2002016-06-22 17:21:13.613 Learn-IOS[24089:546819]  6 
2016-06-22 17:21:14.610 Learn-IOS[24089:546712]  3 
2016-06-22 17:21:17.609 Learn-IOS[24089:546718]  2 

2.dispatch_group_tの使用

dispatch_group_t  ， 

コード:

//DISPATCH_QUEUE_PRIORITY_DEFAULT  
 dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
 dispatch_group_t group = dispatch_group_create();
 dispatch_group_async(group, queue, ^{
 [self downloadTime:7];
 });
 dispatch_group_async(group, queue, ^{
 [self downloadTime:1];
 });
 dispatch_group_async(group, queue, ^{
 [self downloadTime:4];
 });
 dispatch_group_notify(group, dispatch_get_main_queue(), ^{
 NSLog(@" ， UI ， UI");
 });

実行結果:

2002016-06-22 17:26:17.404 Learn-IOS[24231:554422]  1 
2016-06-22 17:26:20.401 Learn-IOS[24231:554436]  4 
2016-06-22 17:26:23.402 Learn-IOS[24231:554430]  7 
2016-06-22 17:26:23.402 Learn-IOS[24231:554388]  ， UI ， UI 

3.dispatch_barrier_asyncの使用

 ， 

コード:

 dispatch_queue_t queue = dispatch_queue_create("lsb", DISPATCH_QUEUE_CONCURRENT);
 dispatch_async(queue, ^{
 [self downloadTime:2];
 });
 dispatch_async(queue, ^{
 [self downloadTime:3];
 });
 dispatch_barrier_sync(queue, ^{
 [self downloadTime:2];
 });
 dispatch_async(queue, ^{
 [self downloadTime:1];
 });

実行結果:

2016-06-22 17:32:13.131 Learn-IOS[24484:564450]  2 
2016-06-22 17:32:14.130 Learn-IOS[24484:564457]  3 
2016-06-22 17:32:20.132 Learn-IOS[24484:564404]  6 
2016-06-22 17:32:20.132 Learn-IOS[24484:564404]  1 

4.dispatch_applyの使用

コード:

// 
dispatch_queue_t queue = dispatch_queue_create("lsb", DISPATCH_QUEUE_SERIAL);
dispatch_apply(5, queue, ^(size_t index) {
    //  5 
    [self downloadTime:index];
});

実行結果:

2016-06-22 17:33:27.505 Learn-IOS[24546:566534]  0 
2016-06-22 17:33:28.506 Learn-IOS[24546:566534]  1 
2016-06-22 17:33:30.507 Learn-IOS[24546:566534]  2 
2016-06-22 17:33:33.508 Learn-IOS[24546:566534]  3 
2016-06-22 17:33:37.509 Learn-IOS[24546:566534]  4 

5.dispatch_onceの使用

 ， 

コード:

 static dispatch_once_t onceToken;
 dispatch_once(&onceToken, ^{
 
 });

6.dispatch_afterの使用

コード:

double delayInSeconds = 2.0;
dispatch_time_t poptime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds*NSEC_PER_SEC);
NSLog(@" ");
dispatch_after(poptime, dispatch_get_main_queue(), ^{
    NSLog(@" ");
});

実行結果:

2016-06-22 17:37:45.208 Learn-IOS[24618:574357]  
2002016-06-22 17:37:47.206 Learn-IOS[24618:574357]