Question

I recently came across a requirement in creating an API for an existing web portal. The current web UI will remain as it is and the API will provide the extra functionality for any clients that would like to build apps on top of the core app.

The web ui is pretty complex and consists of several step-by-step forms to achieve the desired functionality. For instance, some domain object is split into a set of form views (my viewmodel) in a wizard-like fashion. The validation in terms of whether the value entered is an int, whether the email given is valid etc happens on the viewmodel.

I was planning to re-use the viewmodel classes to represent the user input in the api.

e.g. WebUI: public ActionResult Save(FormOne form){…}
API: public ActionResult Save(String apiKey, FormOne form){…}

But this is so difficult i.e. have a perfect mapping between the WebUI viewmodel and the API viewmodel.

What constitutes a good design in this case?

a) Create a new viewmodel for the API?
b) Use the existing viewmodel when possible – create new classes where appropriate
c) Something else?

Thanks,
Y

Answer 1

A ViewModel should only be used by one View.

Don’t reuse them, it is only a source of problems.

Sometimes, we want to violate DRY in order to reduce coupling. This is one of those times.

Make new ViewModels to serve your API.