CRC Cards classresponsibilitycollaborator CRC Cards Wolfgang Pelz 2000

CRC Cards (class-responsibility-collaborator) CRC Cards © Wolfgang Pelz 2000 -04 1

CRC Cards • introduced in 1989 by Kent Beck and Ward Cunningham • designed to teach object oriented programming at Tektronix • a CRC card is an index card in a group setting used to represent: – a class of objects – their behavior – their interactions CRC Cards © Wolfgang Pelz 2000 -04 2

CRC Card format CRC Cards © Wolfgang Pelz 2000 -04 3

CRC definitions • responsibility: knowledge class maintains or service class provides • collaborator: a class whose knowledge or services are needed to fulfill a responsibility CRC Cards © Wolfgang Pelz 2000 -04 4

Methodology • involves a creative exchange: – physical simulation of the workings of the system – participants “become” one or more objects during walk-throughs of typical scenarios – classes are discovered and converted into cards – responsibilities are assigned – collaborators for each responsibility are identified CRC Cards © Wolfgang Pelz 2000 -04 5

Advantages • portable: cards can be used anywhere, even away from the computer or office • anthropomorphic: no computer program can capture the essence of the interactions forced by passing the cards • level of involvement felt by each team member increases • useful throughout the life cycle CRC Cards © Wolfgang Pelz 2000 -04 6

More advantages • provides a basis for more formal analysis and design methodologies • serves as input to a formal method (i. e. , a starting point) • ease the transition from process orientation to object orientation - most formal methods are overwhelming • gives a general bound on the size of a class a card CRC Cards © Wolfgang Pelz 2000 -04 7