Policy Injection in Unity

摘要

In the past two articles, I presented aspect-oriented programming (AOP) using Microsoft Unity 2.0. Formalized in the 1990s as a way to further improve and complement object-oriented programming (OOP), AOP was recently revamped, and many Inversion of Control (IoC) libraries support it. Unity is no exception. The main purpose of AOP is to let developers more effectively deal with crosscutting concerns. In essence, AOP addresses the following question: When you design an object model for an application, how do you deal with aspects of the code such as security, caching or logging? These aspects are key to implementation, but don't strictly belong to the objects in the model you're building. Should you spoil your design to incorporate non-business aspects? Or are you better off decorating your business-oriented classes with additional aspects? If you choose the latter, AOP basically provides a syntax to define and attach these aspects.