diff --git a/app/models/metadata_belongs_to.rb b/app/models/metadata_belongs_to.rb
index 1438c8d..be1fa67 100644
--- a/app/models/metadata_belongs_to.rb
+++ b/app/models/metadata_belongs_to.rb
@@ -13,6 +13,13 @@ class MetadataBelongsTo < MetadataRelatedPosts
     ''
   end
 
+  # Obtiene el valor desde el documento.
+  #
+  # @return [String]
+  def document_value
+    document.data[name.to_s]
+  end
+
   def validate
     super