上传2张图片后，再提交信息到服务器，但是如果uploadImage这个是单例的话信号量就永远在等待了！不知道为什么。
直接贴代码：
dispatch_group_t group=dispatch_group_create();
dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self uploadImage1];
});
dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self uploadImage2];
});
dispatch_group_notify(group,dispatch_get_main_queue(),^{
[self uploadToServer];
});
其中一个uploadImage是,其中：RKUploadImage是一个单例模式的图片上传工具：
dispatch_semaphore_t semaphore=dispatch_semaphore_create(0);
NSString *filename=[NSString stringWithFormat:@"%@_1.png",[RKMineUtils getTimeAndRandom]];
[[RKUploadImage shareUploadImage] uploadImage:img1 name:filename success:^(NSString *imageURL, NSString *imagerURLBase64) {
//计数器+1
imgUrl1=imagerURLBase64;
NSLog(@"上传第一张图片成功");
} failure:^(NSError *error) {
dispatch_semaphore_signal(semaphore);
[self.navigationController.view makeToast:@"身份证上传失败，请重试!"];
[self hideHUD];
}];
//如果是0则等待;
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
求大神指导！
