Visual Basic Design Patterns: VB 6.0 and VB.NET

Chapter 12. The Singleton Pattern

In this chapter, we'll take up the Singleton pattern. This pattern is grouped with the other creational patterns, although it is to some extent a pattern that limits the creation of classes rather than promoting such creation. Specifically, the Singleton assures that there is one and only one instance of a class, and it provides a global point of access to it. There are any number of cases in programming where you need to make sure that there can be one and only one instance of a class. For example, your system can have only one window manager or print spooler, or a single point of access to a database engine. Your PC might have several serial ports, but there can be only one instance of “COM1.”

Creating Singleton ...