Hands-On Design Patterns with C++

Summary

In this chapter, we have learned pretty much all there is to know about the singleton, which is a classic object-oriented programming pattern. We have discussed when to consider using the singleton pattern, and when it should be avoided as a sign of a sloppy design. We have considered several possible implementations of the singleton: some are lazily initialized on demand, and others are eagerly initialized up front; some use multiple handle objects that are all equivalent, and others explicitly present the programmer with the single object. We have considered and compared the thread-safety and performance issues with the different implementations and reviewed the potential issues with the order of construction and destruction.