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Cohesion

• What makes a good class?
  • A class should represent a single concept.
    • Point
    • Circle
    • Time
    • Product
    • Employee
  • Class names should be nouns (function names should be verbs).
• What makes a bad class?
• • If you can't tell from the class name what an object of the class is supposed to do, then you are probably not on the right track.
  • Example: What does a instance of a PaycheckProgram class do?
  • Do not turn an action into a class.
  • Example: ComputePaycheck is a function, not a class.
• The member functions and constants that the public interface of a class expose should be cohesive - all interface features should be closely related to the single concept that the class represents.
• If a class interface refers to multiple concepts, then that is a good sign that it may be time to use separate classes instead.

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