CRC-Cards and Roleplay Diagrams Informal Tools to Teach OO Thinking

CRC-cards (Class,Responsibility andCollaborator) are a lightweight approach to collaborative object-oriented modelling that has been developed as a tool for teaching object-oriented thinking to programmers [1]. They have been used widely in various teaching and training contexts [2, 6, 7, 10]. A CRC-card (see gure 1) corresponds to a class. A responsibility is something the objects of a class know or do as a service for other objects. A book object in a library application, for example, might, among other things, be responsible for checking itself out and knowing its title and due date (see Book in 1). The responsibilities of the objects of a class are written along the left side of the card. A collaborator is an object of another class helping to ful l a speci c responsibility. A book object, for example, can only know whether it is overdue, if it also knows the current date. In gure 1 this information is provided by a collaborator object of class Date. The class names of collaborators are written along the right side of the card. The back of the card can be used for a brief description of the class' purpose, comments and miscellaneous details.