Sinatra CRUD App

meikay profile image meikay ・3 min read

How to build a CRUD app using Sinatra and MVC?

My Homework Log app is made for users to be able to log in/signup/logout of a homework assignment as well as be able to edit and delete their homework assignments.

MVC Structure

Before diving into the project, I thought about what my MVC would look like. What type of data do I need in my models? How do I set up my routes and connect everything in my controllers? And what would all this look like in my views? Instead of building out the MVC structure from scratch, I used a gem named Corneal created by Brian Emory which scafolds the MVC structure for you. It’s simple installation makes set up a breeze!

I built a User model and a Homework_assignment model for my project.

Active Record Associations

For this project, we were required to use at least one has_many relationship on a User model and one belongs_to relationship on another model. Each user has_many homework assignments and each homework assignment belongs_to a user.

Password Encryption

Password encryption was required to protect user accounts from getting hacked. It uses a hashing algorithm to scramble and salt passwords. In order to implement this we installed a gem called bcrypt and my User’s table had a password_digest column. I then added has_secure_password to my User model and now have all the functionalities of the bcrypt gem.

Database Migrations

We’ve been using SQLite for our projects so far which is light weight and simple to use. In db/migrate I created a users table and a homework_assignments table to which I added the data that was needed to make this app usable. I ran rake db:migrate to create a schema file which is a graphical depiction of your database.

Render your View

At this point, we should test out our app adding get '/' do erb:index end to your application_contoller.rb . we should see a welcome page that states everything has been setup up successfully if you’re using Corneal.


I built three controllers which include the application_controller, a homework_assignments_controller and a users_controller. They all contain the necessary routes to help the user sign-in/sign-out, sign-up, and edit.


We use the action and method attributes in HTML to connects to the /signup and post routes in the controllers.

Profile Page

It’s time to be redirected to the user’s profile page. This happens when iterating over the user object and then set the dynamic route to print out the user name of the current user using the user.username route.


To support PATCH and DELETE method types, you would need to add Rack::MethodOverride inside of the config.ru file. Secondly, set up the input like so .

Ensure User can only edit and delete their own content

At this point, I need to search for the saved user ID in the database that matches the entered username and displays the user’s Homework assignments matching the username.

Validate User’s data input

In order for the user to be redirected after signing up, their input needs to be validated so that bad data does not get saved into the data base which will cause problems down the road. I decided to use active record for this where in the models/user.rb I added

validates :username, presence: true
validates :username, uniqueness: true

Posted on Oct 24 '19 by:

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