Factor implementation differences into subcomponents

This is Rule 10 in Johnson and Foote 1988.

If different subclasses implement a method in one of a few ways, then the method may not be directly related to the superclass and the implementation should be separated by creating a class hierarchy and composing it within the superclass.

This means that multiple subclasses can contain the same implementation without repeated code.

An interesting point to note is that this rule is an early version of the Gang of Four Strategy pattern, obviously influenced by Johnson's contribution to the paper.

Example

To do.

See Also

• Strategy
• Johnson and Foote 1988
• Don't repeat yourself