Refactor code: Use correct code pattern

app/repositories/orient_db/learning_object_repository.rb

@@ -8,7 +8,7 @@ module OrientDb
     end
 
     def get_by_dspaceid(id_dspace)
-      result = OrientDb::Client.instance.query "SELECT FROM LearningObject WHERE id_dspace=#{id_dspace}"
+      result = connection.query "SELECT FROM LearningObject WHERE id_dspace=#{id_dspace}"
       return initialize_learning_object result.first
     end
 
@@ -33,15 +33,15 @@ module OrientDb
     end
 
     def find_by_id(rid)
-      @connection.query "SELECT FROM User WHERE @rid=#{rid}"
+      connection.query "SELECT FROM User WHERE @rid=#{rid}"
     end
 
     def author_of(rid)
-      @connection.query "SELECT expand(in) FROM (SELECT expand(out_author_of) FROM User WHERE @rid=#{rid})"
+      connection.query "SELECT expand(in) FROM (SELECT expand(out_author_of) FROM User WHERE @rid=#{rid})"
     end
 
     def has(rid)
-      @connection.query "SELECT expand(in) FROM (SELECT expand(out_has) FROM User WHERE @rid=#{rid})"
+      connection.query "SELECT expand(in) FROM (SELECT expand(out_has) FROM User WHERE @rid=#{rid})"
     end
 
   end