c# - What exactly is "interface based programming"?

Question

I often hear/read about interfaced based programming but I am not exactly clear on what that really means. Is interfaced based programming an actual stand alone topic that actually has books written about it? If so, can anyone recommend any good ones?

I came across interface based programming as I was reading about how good APIs are designed and would like to learn more about it. Right now I am not clear how to properly go about designing an API around interfaces.

Any info is greatly appreciated.

Answer 1

It's basically a matter of expressing your dependencies in terms of interfaces instead of concrete classes (or worse, static methods). So if one of your classes needs to perform authentication, it should be provided an IAuthenticator (or whatever).

This means that:

• You can write your code before implementing the real dependency
• You can test via mocking really easily (without having to mock classes, which gets ugly)
• It's clear what you depend on in terms of the API instead of implementation (i.e. you have looser coupling)