Class hierarchies should be deep and narrow
From CSSEMediaWiki
(Difference between revisions)
| Line 7: | Line 7: | ||
== See also == | == See also == | ||
* [[Favour deep heirarchies]] | * [[Favour deep heirarchies]] | ||
| + | * [[Design maxims]] | ||
Revision as of 03:44, 6 October 2008
A good class hierarchy design should be several layers deep. In a good design, a base class should not have large number of direct children classes (i.e. a superclass has 28 subclasses). If a class hierarchy is not deep but very wide, it is a sign that a change is needed.
Solution for solving this problem is to find some common behaviors from the children sibling classes, and then extract these common behaviors into a parent class under the original base parent class.
Riel's heuristic Favour deep hierarchies is derived from this idea.
