Question

I am using Ruby on Rails 3 and I am trying to use the Rack. Since I am not expert in this matter, I would like to know some thing about that.

The following code is from here.

require 'rack'

class Rack::ForceDomain
  def initialize(app, domain)
    @app = app
    @domain = domain
  end

  def call(env)
    request = Rack::Request.new(env)
    if @domain and request.host != @domain
      fake_request = Rack::Request.new(env.merge("HTTP_HOST" => @domain))
      Rack::Response.new([], 301, "Location" => fake_request.url).finish
    else
      @app.call(env)
    end
  end
end

• What is the variable app and from where its values are retrieved?

• From where and how to pass the domain variable in the initialize method?

Answer 1

Rack is a middleware to interface a higher level app (like rails) to a webserver (like mongrel). In rails, you can get this code to work by using:

# config.middleware.use "Rack::ForceDomain", "mydomain.com"

App is a reference to the Rails instance. Domain is added by the person you got that code from, it is not standard Rack initialize.

You do not need to go down to the rack level for what you are doing though for this. I personally prefer to do the rewrite through nginx, but you can do it in rails 3.

In your config/routes.rb file:

    constraints(:host => /example.com/) do
      root :to => redirect("http://www.example.com")
      match '/*path', :to => redirect {|params| "http://www.example.com/#{params[:path]}"}
    end

This is from http://railsdog.com/blog/2010/10/29/redirect-non-www-requests-the-rails3-way/