Refactoring Workbook

Chapter 9. Inheritance

The relationship between a class and its subclass often starts being simple but gets more complicated over time. A subclass will often depend on its parent more intimately than will a separate class, but it can go too far.

A key challenge is deciding what a class is versus what a class has. A class structure often starts with inheritance and moves to a more compositional style over time.

Smells Covered

• Refused Bequest

• Inappropriate Intimacy (Subclass Form)

• Lazy Class

See also these other smells related to inheritance:

• Simulated Inheritance (Switch Statement), Chapter 7

• Parallel Inheritance Hierarchies, Chapter 11

• Combinatorial Explosion, Chapter 11

Refused Bequest

Symptoms

• A class inherits from a parent, but throws an exception instead ...