Addison Wesley: Modern C++ Design: Generic Programming and Design Patterns Applied by By

Author:By
Language: eng
Format: epub
ISBN: 0-201-70431-5
Publisher: Addison Wesley
Published: 2011-10-03T15:23:26.443977+00:00

6.10 Putting It All Together

This chapter has wandered around various possible implementations of Singleton, commenting on their relative strengths and weaknesses. The discussion doesn't lead to a unique implementation because the problem at hand is what dictates the best Singleton implementation.

The SingletonHolder class template defined by Loki is a Singleton container that assists you in using the Singleton design pattern. Following a policy-based design (see Chapter 1), SingletonHolder is a specialized container for a user-defined Singleton object. When using SingletonHolder, you pick the features needed, and maybe provide some code of your own. In extreme cases, you might still need to start all over again謡hich is okay, as long as those are indeed extreme cases.

This chapter visited quite a few issues that are mostly independent of each other. How, then, can Singleton implement so many cases without utter code bloating? The key is to decompose Singleton carefully into policies, as discussed in Chapter 1. By decomposing SingletonHolder into several policies, we can implement all the cases discussed previously in a small number of lines of code. By using template instantiation, you select the features needed and don't pay anything for the unneeded ones. This is important: The implementation of Singleton put together here is not the do-it-all class. Only the features used are ultimately included in the generated code. Plus, the implementation leaves room for tweaks and extensions.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.