Patterns for Encapsulating Class Trees by Dirk Riehle Union Bank of Switzerland Introduction

In: Pattern Languages of Programm Design 2. Chapter 6. Edited by John M. Vlissides, James O. Coplien and Norman L. Kerth. Reading, Massachusetts: Addison-Wesley, 1996. Good object-oriented design firmly relies on abstract classes. They define the interface to work with subclasses that implement them. If clients directly name these subclasses, they become dependent on them. This complicates both system configuration and evolution. The patterns of Late Creation and Class Retrieval presented in this paper overcome these problems by encapsulating class trees behind their root classes. Clients use class specifications to retrieve classes and create objects. Classes can be removed and plugged into the class tree more easily. Thus, encapsulating class trees eases system evolution and configuration of system variants.