title: SDWebImage Download image and store to cache for key
body: <p>Hello I am using the SDWebImage framework in a project and I want to download and cache images, but I think my code is storing an image in the cache twice?  Is there any way to store the image in the cache by a key only once?  Here is my code.</p>
  
  <pre><code>         SDWebImageManager *manager = [SDWebImageManager sharedManager];
           [manager downloadWithURL:[NSURL URLWithString:url] options:0 progress:^(NSUInteger receivedSize, long long expectedSize) {
  
            } completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished) {
  
              if(image){
                  NSString *localKey = [NSString stringWithFormat:@"Item-%d", i];
                  [[SDImageCache sharedImageCache] storeImage:image forKey:localKey];
              }
  
            }];  
  </code></pre>
  
  <p>Is there something that I missed?  Looks like doing this in my allocations instrument is pilling up a lot of memory.</p>