web service architecture

SUMMARY

Optimally, a flexibleservice architecture must be planned and implemented before the first version of an application is released to achieve its maximum benefits. If one version goes out with hardcoded endpoints or business logic, you are effectively supporting that configuration indefinitely, even if your business greatly evolves from it. With the combination of a remote façade, API versioning, and aservice locator, you have many options to tweak business logic and API settings for apps already in the wild. It becomes easier to support minor tweaks in production code and major new features in upcoming versions without breaking the previous application versions. The upfront development costs of the service infrastructure may seem unnecessary, but it can pay for itself many times over as the application grows and evolves.

简而言之：服务版本号问题、客户端和服务端分离的好处

Professional iOS Network Programming: Connecting the Enterprise to the iPhone and iPad