QBImagePickerController 不可选择照片流中照片

因为QBImagePickerController使用的ALAssetsLibrary方式来读取图片，如果采用默认方式去执行，那么根据url读取到的asset会为空，这时候我们就 需要特殊处理

  [self.assetsLibrary assetForURL:selectedAssetURL
                             resultBlock:^(ALAsset *asset) {
                                 // Add asset

                                 //普通照片方式
                                 if (asset) {
                                     [assets addObject:asset];
 //                                     Check if the loading finished
                                     if (assets.count == weakSelf.selectedAssetURLs.count) {
                                         // Delegate
                                         if (self.delegate && [self.delegate respondsToSelector:@selector(imagePickerController:didSelectAssets:)]) {
                                             [self.delegate imagePickerController:self didSelectAssets:[assets copy]];
                                         }
                                     }
                                 }
                                 //照片流方式
                                 else{
                                     //照片流的处理方法
                                     [self.assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupPhotoStream usingBlock:^(ALAssetsGroup *group, BOOL *stop)
                                      {
                                          [group enumerateAssetsWithOptions:NSEnumerationReverse usingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {

                                              if ([result.defaultRepresentation.url isEqual:selectedAssetURL]) {
                                                  [assets addObject:result];
                                                  *stop = YES;
 //                                                  Check if the loading finished
                                                  if (assets.count == weakSelf.selectedAssetURLs.count) {
                                                      // Delegate
                                                      if (self.delegate && [self.delegate respondsToSelector:@selector(imagePickerController:didSelectAssets:)]) {
                                                          [self.delegate imagePickerController:self didSelectAssets:[assets copy]];
                                                      }
                                                  }
                                              }
                                          }];
                                      } failureBlock:^(NSError *error) {
                                          DDLogVerbose(@"Cann't found asset from stream:%@",[error localizedDescription]);
                                      }];

                                 }
                             } failureBlock:^(NSError *error) {
                                 NSLog(@"Error: %@", [error localizedDescription]);
                             }];