How do I manage registrations on a different domain than my Rails app?

Question

So I have a Rails app at www.myapp.com, and I have a marketing landing page at www.marketingpage.com.

What I want to happen is, when people fill out a registration form on my marketing page, for it to be managed by my Rails app.

I am thinking of just creating a view at myapp.com/mktg, then just having www.marketingpage.com redirect to myapp.com/mktg.

But, the issue with that approach is that I don't want users to see a different domain name for the registration.

How can I approach this, so that the registration on the marketing page looks and feels like it is a full 'mini-site', but it is powered by my main Rails App?

Thanks.

Edit 1

Another thing is, for the registration page at marketingpage.com, I want to use email sign-up only for Devise - so the marketingpage.com is not just 1 page. It will be 1 page, then they at least 1 or 2 more pages. So whatever domain/routing strategy, has to account for that too.

Answer 1

If you have an email input:

<input id="email"></input>
<button id="submit-email"></button>

you can send a jsonp (to get around same-origin restrictions) request when the button is clicked:

$('#submit-email').click(function() {
    submitted_email = $('#email').value()

    // client-side validations

    $.ajax({
        type: 'POST',
        dataType: 'jsonp',
        url: "http://www.myapp.com/signup",
        data: { user: { email: submitted_email } },
        success: function(data) {
            // signup success
        }
    });
});

On the rails end:

class UserController
    def signup
        @user = User.create(params[:user])
        // handle success/failure
        respond_to do |format|
            format.js { render :json => @user }
        end  
    end
end

To retrieve a list of users:

    $.ajax({
        type: 'GET',
        dataType: 'jsonp',
        url: "http://www.myapp.com/users",
        success: function(data) {
            // populate a list
        }
    });