Nil or export coupling only

Riel's Heuristic #2.7

Classes should have only nil or export coupling with other classes. Classes should only depend on the public methods of another class or nothing at all. Other forms of coupling give away implementation details of a class, which is bad for maintenance when implementations need to be changed.

Riel also states that class cohesion ensures that all elements off a class are related.

See also

• Riel's heuristics
• Program to the interface not the implementation
• Design by contract