使用GCD處理多線程,在多核心CPU下,會提高執行效率,下面是一段在項目中使用的GCD代碼。
- - (void)gcdDownload
- {
- static dispatch_once_t once;
- static dispatch_queue_t queue;
- //create download queue
- dispatch_once(&once, ^{
- queue =dispatch_queue_create("com.xxx.download.background",DISPATCH_QUEUE_CONCURRENT);
- });
- //__block type
- __block BOOL downloadFlag = NO;
- dispatch_async(queue, ^{
- // downloadFlag = [Download sendRequest:request];
- NSLog(@"長時間任務,如網絡下載");
- });
- dispatch_barrier_async(queue,^{
- if (downloadFlag) {
- NSLog(@"下載成功完成");
- }
- dispatch_async(dispatch_get_main_queue(), ^{
- NSLog(@"執行完下載,回掉回主線程,例如刷新UI");
- });
- });
- }
可以向queue裏放多個併發block。