Object-oriented design anti-patterns

Revision as of 10:27, 23 September 2009

Object-oriented design anti-patterns describe bad design solutions to common problems. As such, they are essentially the opposite of conventional design patterns.

Many of these anti-patterns are closely related to common design maxims.

The following are common object-oriented design anti-patterns:

Architecture Anti-patterns

• Anemic Domain Model - This anti-pattern occurs when data and behaviour is separated in the domain model.
• BaseBean - This anti-pattern occurs when inheritance for implementation is used; that is a class inherits from another class not because it makes sense semantically but because it wants to use methods defined in the superclass.
• Boat anchor - A piece of software or hardware in the system that serves no useful purpose.
• Call super - This anti-pattern occurs when a superclass requires derived classes to call an overridden method.
• Circle-ellipse problem - This anti-pattern occurs when inheritance is not used correctly and the Liskov substitution principle is violated.
• Circular dependency - This anti-pattern occurs when there are two or more modules that depend directly or indirectly on each other.
• Constant interface - This anti-pattern occurs when an interface is used to declare constants but does not contain any methods.
• Cut and paste programming - Code reused by copying source from other locations. Increasing the likelihood of errors and decreases maintainability.
• Functional decomposition - Classes that resemble the structure of programs creating using functional languages.
• God object - This anti-pattern occurs when an object / class does or knows too much.
• Object cesspool - This anti-pattern occurs when an object pool is used incorrectly in that the state of objects is not reset when they are returned to the pool.
• Object orgy - This anti-pattern occurs when objects access each other internals directly rather than going through methods.
• Poltergeists - This anti-pattern occurs when temporary objects are used to initialize or call methods on more permanent objects.
• Sequential coupling - This anti-pattern occurs when a class requires clients to call methods in a particular order.
• Spaghetti code - An adhoc structure that is difficult to extend and maintain.
• The Blob - Equivalent to God object, a very large class with a functional structure.
• Yo-yo problem - This problem occurs with deep inheritance hierarchies, where a programmer has to keep looking up and down the hierarchy to understand the flow of control of the program.

Development & Management Antipatterns

• Lava Flow - Dead and forgotten code that hardens and becomes unchanged as the system develops. Requires a change in development strategy.
• Mushroom management - This occurs when developers are separated from the end users.
• Golden hammer - When a single technique is applied "obsessively" to software problems.

See also

• Antipatterns
• Design patterns