My class "Product extends DataObject" is shown in a ComplexTableField in the backend. I defined the fields to popup in the fifth parameter of the ComplexTableField:

        $productDetails = new FieldSet(
            new TextField('name', 'Name'),
            new TextareaField('shortDescription', 'Kurzbeschreibung'),
            new TextareaField('description', 'Beschreibung'),
            new SimpleImageField('image', 'Bild'),
            new FileIFrameField('pdf', 'Datenblatt'),
            new DropdownField('manufacturerID', 'Hersteller', $IDandName),
            new CheckboxSetField('mountingmode', 'Montageart', $IDandMountingMode)
            );

The popup "Show" shows values for all fields exept for the new FileIFrameField('pdf', 'Datenblatt'). The popup "Edit" shows the uploaded file. "pdf" is a relationship of "Product":

    static $has_one = array(
        'manufacturer' => 'Manufacturer',
        'categories' => 'Category',
        'image' => 'Image',
        'pdf' => 'File'

How can I get the filename as the value of the popup "Show"?