Chapter 6. Ways To Create Complexity: Break Your API
An API is a sort of a promise…"You can always interact with our program this way, safely and exactly like we said." When you release a new version of your product that doesn't support the API from your old version, you're breaking that promise.
Above and beyond any vague philosophical or moral considerations about this, the technical problem here is that this creates complexity.
Where once users of your API only had to call a simple function, now they have to do a version check against your application and call one of two different functions depending on the result. They might have to pass their parameters a totally different way now, doubling the complexity of their code if they keep both the old way and the new way around. If you changed a lot of functions, they might even have to re-work their whole application just to fit with the way your new API works!
If you break your API several times, their...
