当需要等某几个网络请求提交之后再做某事

/**
 GCDgroup
 */
- (void)GCDgroup
{
dispatch_group_t group = dispatch_group_create();
dispatch_queue_t queue = dispatch_queue_create(0, 0);

NSMutableArray *arr = [NSMutableArray array];

for (int i = 0; i < 10; i++) {
    arr[i] = [NSString stringWithFormat:@"%d",i];
}

for (int i = 0; i < 10; i++) {
    dispatch_group_async(group, queue, ^{
        
        if (i == 5) {
            [NSThread sleepForTimeInterval:3.0];
            EKNSLog(@"第%d个上传任务,等待3秒",i);
            
        } else {
            EKNSLog(@"第%d个上传任务",i);
            [arr removeObjectAtIndex:10-(i+1)];
        }
    });
}


dispatch_group_notify(group, queue, ^{
//        EKNSLog(@"全部上传完了");
    
    for (int i = 0; i < arr.count; i++) {
        EKNSLog(@"%@",arr[i]);
    }
    
});

  EKNSLog(@"----");
}