Teaching Object Oriented Modelling with Crc-cards and Roleplaying Games

CRC-cards have been adopted by many educators to teach early design in their object-oriented programming courses. In this paper we discuss our experiences using the CRC-card approach in upper secondary school and undergraduate programming courses. Although our experiences are generally positive, we have noticed many problems and issues that have largely gone unnoticed in the literature. It is therefore important to apply the CRC-card approach very carefully to avoid building up or reinforcing misconceptions about object-orientation. In this paper we discuss two issues in details. One issue belongs to unintentionally mixing of learning goals. The other issue is the usage of CRC-cards as object surrogates during the scenario roleplay, which is a major source for class/object confusion. To avoid these problems, we introduced a new type of diagram to support the roleplay activities. We also propose to carefully distinguish two steps: Introducing the approach and the notations, and actually using CRC-cards as a modelling tool. The first step aims to introduce the CRC-cards approach itself and the use of CRC-cards to achieve a basic understanding of object oriented concepts. The cards are used as a learning medium to foster object-oriented thinking. In the second step, CRC-cards are used to gain understanding of a domain, learn how to analyse and conceptualise a domain, test a model with roleplay and to introduce more specific object-oriented concepts.