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Smalltalk Report, November–December, 1993
Published online by Cambridge University Press: 04 August 2010
Okay, back to tilting at windmills. Sometimes I think people just don't get Smalltalk. Why in the world would you want a grungy old explicit case statement when you have a superior substitute in the polymorphic message? How could you read and write Smalltalk code for enough years to be able to implement new language features and not understand that you didn't need them?
I guess my tights and cape aren't far enough at the back of the closet…
This month's topic is case statements: practical necessity or pernicious contaminant? My interest in the topic comes from several areas at once. SmalltalkAgents has added a form of case statement to their Smalltalk for the Macintosh. CompuServe has hosted a lively discussion of isKindOf: and its relatives. Finally, net news has had a discussion of case statements. What's the deal?
Cutting right to the punch line, I think case statements are an inappropriate holdover from procedural thinking. While vital in procedural languages, their use in object programs is obviated by the much more powerful mechanism of the polymorphic message send. Anytime you find yourself wishing for or using a case statement, you have an opportunity to take advantage of objects instead. The noncase version will yield a more maintainable, more flexible, more readable, and faster solution.
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