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MCV in Rails and RESTful Routes

Build a small application to display students and their achievements using MVC architecture, RESTful routes, and relationships.

Setup

  • rails new student-manager
  • rails generate model Student first_name:string last_name:string birthdate:date
  • rake db:migrate
  • go into the rails console to generate a few students:
$ rails console
2.1.1 :001 > Student.create(first_name: "StudentA", last_name: "ExampleA")
# You should see '(0.1ms)  begin transaction'... 
2.1.1 :002 > Student.create(first_name: "StudentB", last_name: "ExampleB")
# You should see '(0.1ms)  begin transaction'... 
2.1.1 :003 > Student.create(first_name: "StudentC", last_name: "ExampleC")
# You should see '(0.1ms)  begin transaction'... 
2.1.1 :003 > exit

Displaying Students

  • generate a students controller
  • add get '/students', to: 'students#index in the config/routes.rb to create your route that will show all students
  • add get '/students/:id', to: 'students#show in the config/routes.rb to create your route that will show one particular student
  • add methods in the controller for index and show
  • use @students = Student.all in the index action
  • use @student = Student.find(params[:id] in the show action
  • add an index view and iterate over @students to display every student in the database
  • add a show view and display the data for @student
  • start your Rails server by typing rails s in the command line
  • navigate to localhost:3000/students and verify that all sample students are shown
  • navigate to localhost:3000/students/1 and verify that the first sample student is shown

Setting Up Relationships

Tomorrow we'll be discussing database relationships. In order to prepare, let's add another table to our database: Achievements.

A student can have many achievements, and an achievement belongs to a student. Because of this, we'll store the foreign key on the achievements table.

  • rails generate model achievement description:string awarded_on:date student_id:integer
  • rake db:migrate
  • go into the rails console to generate a few achievements:
$ rails console
2.1.1 :001 > Achievement.create(description: "Mastered MVC in Rails", awarded_on: Date.today, student_id: 1)
# You should see '(0.1ms)  begin transaction'... 
2.1.1 :002 > Achievement.create(description: "Mastered RESTful routing in Rails", awarded_on: Date.today, student_id: 1)
# You should see '(0.1ms)  begin transaction'... 
2.1.1 :003 > Achievement.create(description: "Successfully set up relationships between two tables in Rails", awarded_on: Date.today, student_id: 2)
# You should see '(0.1ms)  begin transaction'... 
2.1.1 :004 > Achievement.create(description: "Generated models and controllers from the command line", awarded_on: Date.today, student_id: 2)
# You should see '(0.1ms)  begin transaction'... 
2.1.1 :003 > exit
  • We're not concerned with displaying achievements separately for right now, so skip over generating a controller and views for achievements.
  • Instead, let's set up relationships
  • Modify student.rb to look like this:
class Student < ActiveRecord::Base
  has_many :achievements
end
  • in the achievement.rb model, add this line:
class Achievement < ActiveRecord::Base
  belongs_to :student
end
  • Now, modify your show.html.erb student view to also display their achievements. When you type student.achievements, you'll get back an array of the achievements that are associated with that student. In the view, iterate through these to display the description and date the achievement was awarded.

Optional Extension

Can you generate an achievements controller and corresponding views so that we can enter achievements through the web interface? Refer back to Blogger for help creating a form in Rails.