We'll review the file structure we'll be using for our MVC Sinatra applications.
appdirectory and create new files and add code to these folders
We could, if we wanted to, write our entire app in a single file. As you might imagine, this would make things very difficult to read and debug.
Keeping our code organized is crucial when developing complex applications.
This concept is called
separation of concerns and
Each file in our application will have a different responsibility and we'll
keep these responsibilities split up into reasonable chunks.
You'll be coding along in this lesson so fork and clone this lab. There are tests to run to make sure your solutions are working. Find the instructions underneath the descriptions for each file you'll be editing.
Take a look at the file structure in this directory. It's okay if it feels overwhelming at first. We're going to walk through the different files and folders and discuss what their responsibilities are.
├── Gemfile ├── README.md ├── app │ ├── controllers │ │ └── application_controller.rb │ ├── models │ │ └── model.rb │ └── views │ └── index.erb ├── config │ └── environment.rb ├── config.ru ├── public │ └── stylesheets └── spec ├── controllers ├── features ├── models └── spec_helper.rb
This holds a list of all the gems needed to run the application. The bundler
gem provides us access to a terminal command:
bundle install. Bundler will
look in the Gemfile and install any gems, as well as any gem dependencies for
Go ahead and enter this command in terminal. It will create a
file for you, which is just a documentation of the specific gem versions that
should be installed.
This folder holds our MVC directories -
We spend most of our time coding in this directory.
This directory holds the logic behind our application. Typically, these files
represent either a component of your application, such as a User, Post, or
Comment, or a unit of work. Each file in models typically contains a different
class. For example,
dog.rb would contain a class called
Dog. As you might
have guessed, models represent the "M" components of the MVC paradigm.
Models represent the data and object logic of our application.
Create a new file in the models directory to create a dog class. This class
should have name, breed, and age attributes which can be set on initialization.
You should be able to read and write to these attributes. This class should
also keep track of each instance of dog created, as well as a class method
all to return an array of those instances.
The controllers, such as
application_controller.rb, are where the application
configurations, routes, and controller actions are implemented. There is
typically a class, which in this case we will call
that represents an instance of your application when the server is up and
application_controller.rb file represents the "C" components of
the MVC paradigm.
(In some simple applications –– including several labs and code-alongs in this
track –– the Application Controller will simply be called
app.rb and will
live in the root directory of the project.)
Sometimes our other controllers will use
ApplicationController as an
inheritance point so that they inherit all the defaults and behaviors defined
in our main
ApplicationController. Other times our other controllers will
simply inherit from
Controllers represent the application logic, generally; the interface and flow of our application.
Let's go ahead and fill in our controller. You'll notice in
application_controller.rb, we have an
ApplicationController class that
Sinatra::Base. When we start up a server, the server will spin
up an instance of the
ApplicationController class to run our app.
You'll also notice there is a
configure block already in the controller. This
configure block tells the controller where to look to find the views (your
pages with HTML to display text in the browser) and the public directory.
When a client makes a request to a server to load an application, the request is received and processed by the controller. We need to set up a controller action to accept the request and respond with the appropriate HTML.
We've created a controller action that can receive and respond to a
request to the root URL
GET request loads the
This directory holds the code that will be displayed in the browser. In a
Sinatra app we use
.erb files instead of
.html files because .erb files
allow us to include regular, old HTML tags AND special erb tags which contain
Ruby code. We can name them anything we like, but by convention, our file names
will match up with the action that renders them. For example, a GET request
/ typically renders a file called
Views represent how things look and are displayed in our application. We've
created a file
index.erb that contains some basic HTML code.
We've already told the controller how to load this file in the view.
config.ru file is necessary when building Rack-based applications and using
shotgun to start the application server (the ru stands for rackup).
config.ru is first responsible for loading our application environment, code,
Once all our code is loaded,
config.ru then specifies which controllers to
load as part of our application using
In this case, our
config.ru file contains the line
run ApplicationController, which creates an instance of our
ApplicationController class that can respond to requests from a client.
This directory holds an
environment.rb file. We'll be using this file to
connect up all the files in our application to the appropriate gems and to each
environment.rb file loads Bundler and thus all the gems in our Gemfile,
as well as the
public directory holds our front-end assets. In the example above, it
front-end assets (like image files) should also be stored in
spec directory contains any tests for our applications. These tests set
up any expectations for the rest of the project. These are often broken down
into unit tests for models, controller tests for routes, and feature tests,
which check the actual behavior for users.
Don't forget to run your tests!
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