Creating a New Model Class to Associate With
In this demonstration, we will lay the groundwork for the upcoming association demos by creating a new class of model objects, Quiz, to which McQuestion model objects will belong. The tasks in this demo are for the most part repeats of the ones covered in the previous demos, so we will tend to be brief in our explanations of the tasks. We will continue to build upon the QuizMe project from the previous demos.
In particular, we will be updating our model design by adding a new model class, Quiz, as depicted in Figure 1.
Figure 1. The updated database design, including the newly added Quiz model class.
To enable users to perform CRUD operations on Quiz records, we will add the standard Rails resource pages and actions (index, show, new/create, edit/update, and destroy), as depicted in Figures 2–5.
Figure 2. Example index page for Quiz. The “New Quiz” hyperlink goes to the new form for Quiz. The “🔎” hyperlink goes to the show page for the corresponding Quiz record. The “🖋” hyperlink goes to the edit page for the corresponding Quiz record. The “🗑” hyperlink deletes (via the destroy action) the corresponding Quiz record. Note that the description of each Quiz record is truncated such that only the first 75 characters are displayed.
Figure 3. Example show page for Quiz.
Figure 4. Example new form page for Quiz. Like the previous demo on forms for creating model records, submissions of the form are processed by a create controller action.
Figure 5. Example edit form page for Quiz. Like the previous demo on forms for updating model records, submissions of the form are processed by a update controller action.
1. Creating the Quiz Model Class
The tasks in this part were previously introduced in this demo.
Generate the Quiz model class along with a corresponding database migration, like this:
rails g model Quiz title:string description:text
Run the newly generated migration to update the database schema by running the following command:
rails db:migrate
Verify that the database schema was updated correctly by using pgAdmin to inspect the quizzes database table. The table should have no rows of data, but the table should be present, and the columns should be correct.
2. Adding and Testing Valid Fixtures for the Quiz Model Class
The tasks in this part were previously introduced in this demo.
In test/fixtures/quizzes.yml, add a valid test fixture for the Quiz model, like this:
one:
title: Rails Concepts
description: This quiz covers basic Rails programming concepts.
Note that we forgo making a second fixture (two) this time, because we do not anticipate needing a second one for any of our tests.
In test/models/quiz_test.rb, add a test for all the Quiz fixtures to verify that they are all valid, like this:
test "fixtures are valid" do
quizzes.each do |q|
assert q.valid?, q.errors.full_messages.inspect
end
end
Confirm that the tests work and are passing by running the following command:
rails test
We should see 0 failures and 0 errors. If we do see failures or errors, then there is a bug in the code that needs fixing.
3. Adding and Testing presence Validations for the Quiz Model Class
The tasks in this part were previously introduced in this demo.
In the Quiz model class, add presence validations for title and description, like this:
validates :title, presence: true
validates :description, presence: true
In test/models/quiz_test.rb, add tests to verify that title and description must be present (not nil and not a blank string) in order for a Quiz object to be valid, like this:
test "title presence not valid" do
q = quizzes(:one)
q.title = nil
assert_not q.valid?
q.title = ""
assert_not q.valid?
end
test "description presence not valid" do
q = quizzes(:one)
q.description = nil
assert_not q.valid?
q.description = ""
assert_not q.valid?
end
Confirm that the tests work and are passing by running the following command:
rails test
We should see 0 failures and 0 errors. If we do see failures or errors, then there is a bug in the code that needs fixing.
4. Seeding the Database with Quiz Records
The tasks in this part were previously introduced in this demo.
Add a couple of Quiz seeds at the top of the seeds.rb file, like this:
quiz1 = Quiz.create!(
title: 'MVC Concepts',
description: 'This quiz covers concepts related to the Model-View-Controller web application architecture.'
)
quiz2 = Quiz.create!(
title: 'Rails Concepts',
description: 'This quiz covers concepts related to web application development using the Ruby on Rails platform.'
)
Reset and seed the database using the following command:
rails db:migrate:reset db:seed
Verify that the data was seeded correctly by using pgAdmin to inspect the quizzes database table.
5. Creating a Controller for Quiz Records
The tasks in this part were previously introduced in this demo.
Create a QuizzesController by entering this command:
rails g controller Quizzes
6. Adding the index Resource Action for Quiz Records
The tasks in this part were previously introduced in this demo.
Create the standard RESTful route for index for the Quiz model class by adding the following code to the routes.rb file:
get 'quizzes', to: 'quizzes#index', as: 'quizzes' # index
Add the index controller action by inserting a new index method in the QuizzesController class, like this:
def index
# get all quiz objects
quizzes = Quiz.all
# display index view
respond_to do |format|
format.html { render :index, locals: { quizzes: quizzes } }
end
end
Create a new index view in app/views/quizzes/index.html.erb, like this:
<h1>Quizzes</h1>
<% quizzes.each do |quiz| %>
<div id="<%= dom_id(quiz) %>">
<br>
<p>
<%= quiz.title %>
</p>
<p>
<%= truncate quiz.description, length: 75, separator: ' ' %>
</p>
</div>
<% end %>
Note that the truncate method is a handy way to shorten a long string when we want only a brief summary. In particular, the method will return the first length characters of a string followed by an ellipsis (“...”).
Add a link to the index page for Quiz on the app’s home page by inserting a call to the link_to helper above the “About” and “Contact” links in the welcome.html.erb view, like this:
<p><%= link_to "Quizzes", quizzes_path %></p>
Verify that the newly added code works by running the app, opening the app’s home page, and using the new hyperlink to navigate to the index page for Quiz records.
7. Adding the show Resource Action for Quiz Records
The tasks in this part were previously introduced in this demo.
Create the standard RESTful route for show for the Quiz model class by inserting the following code after the index route the routes.rb file:
get 'quizzes/:id', to: 'quizzes#show', as: 'quiz' # show
Add the show controller action by inserting a new show method in the QuizzesController class, like this:
def show
# find a particular object
quiz = Quiz.find(params[:id])
# display the object
respond_to do |format|
format.html { render :show, locals: { quiz: quiz } }
end
end
Create a new show view in app/views/quizzes/show.html.erb, like this:
<h1><%= quiz.title %></h1>
<p>
<%= quiz.description %>
</p>
Add links to the show pages for Quiz records on the index page for Quiz records by inserting a call to the link_to helper after the quiz title in the index.html.erb view, like this:
<p>
<%= quiz.title %>
<%= link_to '🔎', quiz_path(quiz) %>
</p>
Verify that the newly added code works by running the app, opening the app’s index page for Quiz records, and using the new hyperlinks to navigate to the show pages for Quiz records.
8. Adding the new/create Resource Actions for Quiz Records
The tasks in this part were previously introduced in this demo.
Create the standard RESTful routes for new/create for the Quiz model class by inserting the following code after the index route (but before the show route) for Quiz in the routes.rb file:
get 'quizzes/new', to: 'quizzes#new', as: 'new_quiz' # new
post 'quizzes', to: 'quizzes#create' # create
Add the new/create controller actions by inserting a new new method and a new create method in the QuizzesController class, like this:
def new
# make empty quiz object
quiz = Quiz.new
# display new view
respond_to do |format|
format.html { render :new, locals: { quiz: quiz } }
end
end
def create
# new object from params
quiz = Quiz.new(params.require(:quiz).permit(:title, :description))
# respond_to block
respond_to do |format|
format.html do
if quiz.save
# success message
flash[:success] = "Quiz saved successfully"
# redirect to index
redirect_to quizzes_url
else
# error message
flash.now[:error] = "Error: Quiz could not be saved"
# render new
render :new, locals: { quiz: quiz }
end
end
end
end
Create a new new view in app/views/quizzes/new.html.erb, like this:
<h1>New Quiz</h1>
<%= form_with model: quiz, url: quizzes_path, method: :post, local: true, scope: :quiz do |form| %>
<div>
<%= form.label :title %><br>
<%= form.text_field :title %>
</div>
<div>
<%= form.label :description %><br>
<%= form.text_area :description, size: "27x7" %>
</div>
<%= form.submit "Add Quiz" %>
<% end %>
Add a link to the new form page for Quiz records on the index page for Quiz records by inserting a call to the link_to helper after the h1 heading element in the index.html.erb view, like this:
<p>
<%= link_to 'New Quiz', new_quiz_path %>
</p>
Verify that the newly added code works by running the app, opening the app’s index page for Quiz records, using the new hyperlink to navigate to the new form pages for Quiz records, and using the form to create some new Quiz records.
9. Adding the edit/update Resource Actions for Quiz Records
The tasks in this part were previously introduced in this demo.
Create the standard RESTful routes for edit/update for the Quiz model class by inserting the following code after the show route for Quiz in the routes.rb file:
get 'quizzes/:id/edit', to: 'quizzes#edit', as: 'edit_quiz' # edit
put 'quizzes/:id', to: 'quizzes#update' # update (put)
patch 'quizzes/:id', to: 'quizzes#update' # update (patch)
Add the edit/update controller actions by inserting a new edit method and a new update method in the QuizzesController class, like this:
def edit
# object to use in form
quiz = Quiz.find(params[:id])
respond_to do |format|
format.html { render :edit, locals: { quiz: quiz } }
end
end
def update
# load existing object again from URL param
quiz = Quiz.find(params[:id])
# respond_to block
respond_to do |format|
format.html do
if quiz.update(params.require(:quiz).permit(:title, :description))
# success message
flash[:success] = 'Quiz updated successfully'
# redirect to index
redirect_to quizzes_url
else
# error message
flash.now[:error] = 'Error: Quiz could not be updated'
# render edit
render :edit, locals: { quiz: quiz }
end
end
end
end
Create a new edit view in app/views/quizzes/edit.html.erb, like this:
<h1>Edit Quiz</h1>
<%= form_with model: quiz, url: quiz_path, method: :patch, local: true, scope: :quiz do |form| %>
<div>
<%= form.label :title %><br>
<%= form.text_field :title %>
</div>
<div>
<%= form.label :description %><br>
<%= form.text_area :description, size: "27x7" %>
</div>
<%= form.submit "Update Quiz" %>
<% end %>
Add links to the edit form pages for Quiz records on the index page for Quiz records by inserting a call to the link_to helper after the quiz title in the index.html.erb view, like this:
<p>
<%= quiz.title %>
<%= link_to '🔎', quiz_path(quiz) %>
<%= link_to '🖋', edit_quiz_path(quiz) %>
</p>
Verify that the newly added code works by running the app, opening the app’s index page for Quiz records, using the new hyperlink to navigate to the edit form pages for Quiz records, and using the form to update some existing Quiz records.
10. Adding the destroy Resource Action for Quiz Records
The tasks in this part were previously introduced in this demo.
Create the standard RESTful route for destroy for the Quiz model class by inserting the following code after the update actions in the routes.rb file:
delete 'quizzes/:id', to: 'quizzes#destroy' # destroy
Add the destroy controller action by inserting a new destroy method in the QuizzesController class, like this:
def destroy
# load existing object again from URL param
quiz = Quiz.find(params[:id])
# destroy object
quiz.destroy
# respond_to block
respond_to do |format|
format.html do
# success message
flash[:success] = 'Quiz removed successfully'
# redirect to index
redirect_to quizzes_url
end
end
end
Add links to the destroy actions for Quiz records on the index page for Quiz records by inserting a call to the link_to helper after the quiz title in the index.html.erb view, like this:
<p>
<%= quiz.title %>
<%= link_to '🔎', quiz_path(quiz) %>
<%= link_to '🖋', edit_quiz_path(quiz) %>
<%= link_to '🗑', quiz_path(quiz), method: :delete %>
</p>
Verify that the newly added code works by running the app, opening the app’s index page for Quiz records, and using the new hyperlink to delete some existing Quiz records.
We now have a working Quiz model class and CRUD resource pages. In the next demo, we will make the application more interesting by giving each Quiz object an associated set of McQuestion model objects.