-1. Get familiar with OmniAuth by Intridea: github.com/intridea/omniauth. Read about OAuth2.

1. Obtain client_id and client_secret for your app from Exvo.

2. Install exvo-auth gem or add it to your Gemfile.

3. Configure middleware(s).

There are two middlewares. Usually you will need the “interactive” one:

ExvoAuth::Strategies::Interactive
ExvoAuth::Strategies::NonInteractive

Both middlewares need client_id and client_secret arguments. In Rails, the relevant line could look like this:

config.middleware.use ExvoAuth::Strategies::Interactive, "client_id", "client_secret"

1. Add routes.

The following comes from Rails config/routes.rb file:

match "/auth/failure"                  => "sessions#failure"
match "/auth/interactive/callback"     => "sessions#create"
match "/auth/non_interactive/callback" => "sessions#create"

Failure url is called whenever there’s a failure (d’oh). You can have separate callbacks for interactive and non-interactive callback routes but you can also route both callbacks to the same controller method like shown above.

1. Include controller helpers into your application controller.

include ExvoAuth::Controllers::Rails (or Merb)

1. Implement callback(s).

Sample implementation in SessionsController:

def create
  render :text => params[:auth].inspect
end

In short: you get params. Do what you want to do with it: store the data, create session, etc.

1. Read the source, there are few features not mentioned in this README.