title: Thumbnail Association in ios?
body: <p>I am trying to run a cocoapod dependency <a href="https://github.com/Alua-Kinzhebayeva/iOS-PDF-Reader" rel="nofollow noreferrer">ios-PDF-Reader</a> and when I select a pdf on my phone via 'Files' app I get the following error: </p>
  
  <pre><code>[DocumentManager] Failed to associate thumbnails for picked URL file:///private/var/mobile/Containers/Data/Application/../../Welcome.pdf 
  with the Inbox copy file:///private/var/mobile/Containers/Data/Application/../../tmp/com../Welcome.pdf: 
  Error Domain=QLThumbnailErrorDomain Code=102 "(null)" 
  UserInfo={NSUnderlyingError=0x28226cf90 {Error Domain=GSLibraryErrorDomain Code=3 "Generation not found" 
  UserInfo={NSDescription=Generation not found}}}
  </code></pre>
  
  <p>Has anyone gotten the failed to associate thumbnail error before? and is there a simple fix for it? Here is the code where it breaks: </p>
  
  <pre><code>extension TestPdfEpubViewController: UIDocumentPickerDelegate {
      func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
  guard let selectedFileURL = urls.first else { return }
              //create pdf first
              let documentFileURL = Bundle.main.url(forResource: selectedFileURL.absoluteString, withExtension: "pdf")!
              let document = PDFDocument(url: documentFileURL)!
              //then display the pdf
              let readerController = PDFViewController.createNew(with: document)
              navigationController?.pushViewController(readerController, animated: true)
          }
  }
  
  </code></pre>