前言

聊天列表的刷新,消息收取的處理,都是大量數(shù)據(jù)的本地或者內(nèi)存的處理.都可以考慮用dispatch_source_t來優(yōu)化性能.

• 當同一時間，一個事件的的觸發(fā)頻率很高，那么Dispatch Source會將這些響應以ADD的方式進行累積，然后等系統(tǒng)空閑時最終處理，如果觸發(fā)頻率比較零散，那么Dispatch Source會將這些事件分別響應。

@implementation YHRefreshViewController {
    dispatch_source_t _eventUnion;
}


- (void)viewDidLoad {
    [super viewDidLoad];
    _eventUnion = dispatch_source_create(DISPATCH_SOURCE_TYPE_DATA_ADD, 0, 0, dispatch_get_main_queue());
    dispatch_source_set_event_handler(_eventUnion, ^{
        NSLog(@"event Union"); //執(zhí)行
    });
    dispatch_resume(_eventUnion);
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    for (int i = 0; i < 10; i++) {
        dispatch_source_merge_data(_eventUnion, 1);
    }
}


@end

• 上面代碼只會打印一次
  +下面我們來看下DISPATCH_SOURCE_TYPE_DATA_ADD的所有類型

dispatch_source_merge_data()觸發(fā)
1.
/*!
 * @const DISPATCH_SOURCE_TYPE_DATA_ADD
 * @discussion A dispatch source that coalesces data obtained via calls to
 * dispatch_source_merge_data(). An ADD is used to coalesce the data.
 */
#define DISPATCH_SOURCE_TYPE_DATA_ADD
 聯(lián)合頻率比較高的事件,傳遞數(shù)據(jù)會相加

2.
/*!
 * @const DISPATCH_SOURCE_TYPE_DATA_OR
 * @discussion A dispatch source that coalesces data obtained via calls to
 * dispatch_source_merge_data(). A bitwise OR is used to coalesce the data.
 */
#define DISPATCH_SOURCE_TYPE_DATA_OR
 聯(lián)合頻率比較高的事件,傳遞數(shù)據(jù)會按位或

3.
/*!
 * @const DISPATCH_SOURCE_TYPE_WRITE
 * @discussion A dispatch source that monitors a file descriptor for available
 * buffer space to write bytes.
 */
#define DISPATCH_SOURCE_TYPE_WRITE

可以作為定時器,需要dispatch_source_set_timer();