Loading the Application

In this section, we'll see how the app.rb file initializes the application. This file is important in the boot process because it defines everything the application needs in order to run. We'll walk step by step through this file so you understand everything that happens under the hood.

First, we require the gems we'll use in this project.

require "cuba"
require "cuba/mote"
...
require "scrivener"

Then we define some constants that, for example, are used to connect to a database or to check cookie data integrity. Because these are sensitive configurations, we use environment variables instead of putting them directly into the code.

APP_KEY = ENV.fetch("APP_KEY")
APP_SECRET = ENV.fetch("APP_SECRET")
DATABASE_URL = ENV.fetch("DATABASE_URL")

To load these values into our environment, we read them from the .env file when starting the server. Then, we use the ENV object to access them. The fetch method will raise an error if a configuration is not present.

The next part is where we connect Cuba with its friends. We'll have a closer look later.

Ohm.redis = Redic.new(DATABASE_URL)

Cuba.plugin(Cuba::Mote)
Cuba.plugin(Shield::Helpers)

...

Cuba.use(Rack::Protection)
Cuba.use(Rack::Protection::RemoteReferrer)

Next, we require the content of the subfolders where we find the core code of our application. This includes models, filter objects, helpers, etc.

Dir["./models/**/*.rb"].each  { |f| require(f) }
Dir["./filters/**/*.rb"].each { |f| require(f) }
Dir["./helpers/**/*.rb"].each { |f| require(f) }
Dir["./routes/**/*.rb"].each  { |f| require(f) }

Finally, you should recognize the last part:

Cuba.define do
  on root do
    render("home")
  end
end

It's almost the same as in our first example, but with one significant difference: the render method. In the next chapter, we'll explain this method and see how it can be used to render view templates.