Is there a general Cocoa or Cocoa Touch library for interacting with any web service API, or one which can be used as a basis for creating my own library for a web service? For example, I could add some details about how to interact with the Vimeo API (how to verify user details, what URLs to call). I'm not sure how this would work in reality.
If not, can anyone suggest an web service library which I could alter to change the API calls? It would need to be fairly simple (a small API) and easy to adapt. An example is this Cocoa library for Twitter (although it would probably be too complicated to adapt). Would it be easier just to code it up from scratch?
I don't think there is a library that will automagically work with any web API. In fact I don't even think it's possible to write such a library, since you can define your web API any way you want to. That library would have to be pretty smart in order to figure out how to use an arbitrary API.
I think the closest you'll get is something like ASIHTTPRequest, which is a great library for interacting with web services. If you add a JSON and/or XML parser you'll have everything you need to interact with almost any web API.