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Data abstraction, explained in Chapter 14, provides another reason
for using setter and getter methods for class variables. You might
determine, for example, that the value of ProteinRatio must be equal
to the value of CarbohydrateRatio. If you have used setters and
getters for the class variables, you can enforce the equality constraint by
storing just one number accessed by both setter–getter pairs:
Food class definition Object subclass: #Food instanceVariableNames: 'fCalories cCalories pCalories' classVariableNames: 'FatRatio CommonRatio' poolDictionaries: '' Food method definition • class carbohydrateRatio ^ CommonRatio Food method definition • class carbohydrateRatio: aNumber CommonRatio := aNumber Food method definition • class proteinRatio ^ CommonRatio Food method definition • class proteinRatio: aNumber CommonRatio := aNumber