title: SDWebImage load pictures and something about setting HTTP headers
body: <p>I'm facing the problem that every picture has different HTTP headers and I have to set it before downloading:</p>
  
  <pre><code>SDWebImageDownloader *manager = [SDWebImageManager sharedManager].imageDownloader;
  [manager @"value" forHTTPHeaderField:@"key];
  [self.imageView sd_setImageWithURL:[NSURL URLWithString:str]];
  </code></pre>
  
  <p>But when I set many pictures, only the last picture can be loaded. How can I solve this problem?</p>