Add More Classes

• Object-Oriented Design

“When things get too complex, add more classes.”¹⁾

Complexity can often be reduced by adding further classes that better separate concerns.

• Divide larger classes into several smaller ones.
• Use polymorphism, dynamic binding and abstract couplings.

• Adding too many classes leads to ravioli code. Which may be hard to grasp and debug.
• Classes need to be separately understandable (see PSU).

See section contrary principles.

Grady Booch is sometimes cited like that. The precise origin is unknown. See AddMoreClasses.

• High Cohesion (HC): Add more classes is a direct result of HC.

• More Is More Complex (MIMC): Add More Classes decreases complexity with respect to the size of the classes on expense of increased complexity due to the number of classes. There is always a tradeoff to be made. Add More Classes tells that an increased number of classes often is the lesser evil while MIMC explains the tradeoff to be made.

• Encapsulate the Concept that Varies (ECV): ECV tells how to separate concerns when add more classes shall be used to lower complexity.
• Model Principle (MP): While adding classes MP should be considered in order to find appropriate concepts for encapsulation into a class.

Stub

• AddMoreClasses
• FearOfAddingClasses
• HowToAvoidFearOfAddingClasses
• MinimumNumberOfClassesAndMethods
• RavioliCode
• Ravioli code

Discuss this wiki article and the principle on the corresponding talk page.