My Photo Stream (我的照片流)ALAsset return nil

做了一个图片多选的功能,因为要支持iOS6,所以使用了AssetsLibrary遍历读取照片,但是选取我的照片流相册中的照片时,通过NSUrl,即图片的地址读取该照片ALAsset 为nil.
看了一下百度云将我的照片流过滤掉了,360云盘也出现了选取图片为nil 的情况.

google了一下, 以下为解决方法,如果返回为nil的话,需要再重新遍历一次group,将其取出:
<pre><code>

• (void)loadItem:(NSURL *)url withSuccessBlock:(ALAssetsLibraryAssetForURLResultBlock)resultBlock andFailureBlock:(ALAssetsLibraryAccessFailureBlock)failureBlock {
  ALAssetsLibrary *assetslibrary = [[ALAssetsLibrary alloc] init];

  [assetslibrary assetForURL:url
  resultBlock:^(ALAsset *asset)
  {
  if (asset){
  //////////////////////////////////////////////////////
  // SUCCESS POINT #1 - asset is what we are looking for
  //////////////////////////////////////////////////////
  resultBlock(asset);
  }
  else {
  // On iOS 8.1 [library assetForUrl] Photo Streams always returns nil. Try to obtain it in an alternative way

         [assetslibrary enumerateGroupsWithTypes:ALAssetsGroupPhotoStream
                                      usingBlock:^(ALAssetsGroup *group, BOOL *stop)
          {
              [group enumerateAssetsWithOptions:NSEnumerationReverse usingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {
                  if([result.defaultRepresentation.url isEqual:url])
                  {
                      ///////////////////////////////////////////////////////
                      // SUCCESS POINT #2 - result is what we are looking for
                      ///////////////////////////////////////////////////////
                      resultBlock(result);
                      *stop = YES;
                  }
              }];
          }
             failureBlock:^(NSError *error)
          {
              NSLog(@"Error: Cannot load asset from photo stream - %@", [error localizedDescription]);
              failureBlock(error);
              
          }];
     }
  

  }
  failureBlock:^(NSError *error)
  {
  NSLog(@"Error: Cannot load asset - %@", [error localizedDescription]);
  failureBlock(error);
  }
  ];
  }
  </code></pre>