title: silverstripe-translatable: how to make dataobjects translatable (slideshow)?
body: <p>I am creating a multilingual Website in Silverstripe, the goal is to have the whole content available in three languages. I am using the translatable module, works fine for now.</p>
  
  <p>Some pages contains a slideshow, meaning that I am associating a bunch of images and captions to these pages. Looks like this:</p>
  
  <pre><code>class Slide extends DataObject {
  
      private static $db = array(
          'Caption'     =&gt; 'Varchar(255)',
          'SortIndex'   =&gt; 'Int'
      );
  
      private static $has_one = array(
          'ParentPage' =&gt; 'Page',
          'Image' =&gt; 'Image'
      );
  
      public static $default_sort = 'SortIndex';
  
      public function getCMSFields() {
          // parent::getCMSFields() does all the hard work and creates the fields for Title, IsActive and Content.
          $fields = parent::getCMSFields();
          $fields-&gt;dataFieldByName('Caption')-&gt;setTitle('Titel');
          $fields-&gt;dataFieldByName('Image')-&gt;setTitle('Bild');
          $fields-&gt;dataFieldByName('Index')-&gt;setTitle('Reihenfolge');
  
          $fields-&gt;push(new TextField('Caption', 'Titel'));
          $fields-&gt;push(new UploadField('Image', 'Profile Image'));
  
          // Apply Translatable modifications
          $this-&gt;applyTranslatableFieldsUpdate($fields, 'updateCMSFields');
  
          return $fields;
      }
  }
  
  
  class SlideShowPage extends Page {
  
      private static $has_many = array(
          'Slides' =&gt; 'Slide'
      );
  
      public function getCMSFields() {
          $fields = parent::getCMSFields();
  
          $conf = GridFieldConfig_RelationEditor::create(10);
          $conf-&gt;addComponent(new GridFieldSortableRows('SortIndex'));
  
          $fields-&gt;addFieldToTab('Root.Slideshow', new GridField('Slide', 'Slides', $this-&gt;Slides(), $conf));
  
          // Apply Translatable modifications
          $this-&gt;applyTranslatableFieldsUpdate($fields, 'updateCMSFields');
  
          return $fields;
      }
  }
  </code></pre>
  
  <p></p>
  
  <p>I want to make these slideshows translatable as well. Meaning that I want to prepare the slide show once in the primary language, then hit the "create new translation" button, and get the slideshow available in the translated version as well, with the captions ready to be translated (similar as the main text content). According to the <a href="https://github.com/silverstripe/silverstripe-translatable/blob/master/docs/en/index.md#translating-custom-properties" rel="nofollow noreferrer">silverstripe-translatable docs</a> this shall be possible. I have added these calls to <code>applyTranslatableFieldsUpdate()</code> (see in the code above) and added these lines to my _config.php file as well:</p>
  
  <pre><code>SlideShowPage::add_extension('Translatable');
  Slide::add_extension('Translatable');
  </code></pre>
  
  <p>The table <code>Slide_translationgroups</code> is even created successfully and filled with new entries for each translation. But the content of table <code>Slide</code> is not copied.</p>
  
  <p>What am I missing?</p>
  
  <p>Thanks!
  Sacher</p>