General approach to building Rails applications with Devise

I have built a number of complex Rails applications that include user authentication. I want to describe my general approach to getting these up and running.

In most of them I chose the Devise gem to handle authentication and added a number of custom fields to the User model (first name, last name, etc). The gem documentation and this Railscast can help you get started with all that.

One approach is to build your core application without authentication and then add it in at a later stage but I don't like that.

Authentication can quickly get very complicated once you start adding user confirmation via email, an admin role and other custom fields. I prefer to get all that machinery up and running in the context of a very simple application and only then add my real application code into it.

Similarly, when I'm starting with a new application I don't usually hit on the right data architecture right away. That leads to me adding new columns to my database tables and models over time and it always involves quite a lot of 'rake db:rollback / rake db:migrate' operations. I prefer to go through this phase without the extra baggage of authentication, and often, without worrying a lot about CSS etc. I just need to try several alternate views of the problem before I settle on a final design.

So may approach is to build two applications side by side. The first is a minimal application with, say, a single table (usually called 'posts') to which I add Devise and configure all the options that I want.

This is a very useful piece of code for other applications, so I always create a good README and store a copy of the code for future use.

Separately I work through my core application and, once that is working, I condense all the migrations that add/remove/rename columns into a few 'clean', simple migrations.

Finally I add the core application code to the minimal authenticated application. That way it is easier for me to update the controllers, etc. to use authentication.

The bottom line is that you want to minimize the number of moving parts in the early stages of a new application design. This is a simple approach that works very well for me.