Rails ERB Validation - ruby-on-rails

Question

I'm trying to add a validation to my Rails app in order to display an error message if the user goes to the wrong id. The project has reviews, if I go to http://localhost:3000/reviews/:id that doesn't exist the app crashes, I'd like to prevent the runtime error by displaying a message.
In the model, I got this validation:
class Review < ApplicationRecord
validates :id, presence: true
end
Then, in the reviews/show.html.erb file, I'm trying this:
<% if #review.valid? %>
<div class='review-header'>
....
</div>
<% else %>
<% #review.errors.objects.first.full_message %>
<% end %>
This is also the Reviews Controller:
class ReviewsController < ApplicationController
before_action :set_review, only: [:show, :edit, :update, :destroy]
before_action :authorize!, only: [:edit, :destroy]
def index
if params[:search]
#reviews = Review.where("title like ?", "%#{params[:search]}%")
else
#reviews = Review.all
end
end
def new
#review = Review.new
#comment = Comment.new
#comment.review_id = #review.id
#We need to declare the comments in the new action.
end
def create
#review = current_user.reviews.new(review_params)
if #review.save
redirect_to review_path(#review)
else
render 'new'
end
end
def show
#comment = Comment.new
#We also need to declare the new comment in the show action.
end
def edit
end
def update
if #review.update(review_params)
redirect_to review_path(#review)
else
render 'edit'
end
end
def destroy
#review.destroy
redirect_to reviews_path
end
private
def set_review
#review = Review.find_by(id: params[:id])
end
def review_params
params.require(:review).permit(:title, :content, :category_id, :search)
end
def authorize!
authorize #review #authorize method using the Pundit gem
end
end
However, my project keep crashing rather than showing a message. If there's any way I can make this work? Thanks.

Answer 1

The whole setup of the question is actually broken.
You don't need to add a model validation for the id since ids are automatically generated by the database when you insert records. On most databases primary keys are also non-nullable. Adding the validation will actually break the model as will prevent you from saving records without manually assigning an id (bad idea).
Its also not the models job to verify that a record can be found in the controller. Instead your controller should use find so that it bails early if the record cannot be found:
class ReviewsController < ApplicationController
before_action :set_review, only: [:show, :edit, :update, :destroy]
before_action :authorize!, only: [:edit, :destroy]
private
def set_review
#review = Review.find(params[:id])
end
end
This halts execution of the method and other callbacks and prevents the NoMethodErrors that are bound to occur. There is no sense in continuing to process a request if the record that its supposed to CRUD doesn't exist.
By default Rails will handle an uncaught ActiveRecord::RecordNotFound exception by rendering a static HTML page located at public/404.html and returning a 404 status code. If you want to customize this on the controller level use rescue_from:
class ReviewsController < ApplicationController
before_action :set_review, only: [:show, :edit, :update, :destroy]
before_action :authorize!, only: [:edit, :destroy]
rescue_from ActiveRecord::RecordNotFound, with: :not_found
private
def set_review
#review = Review.find(params[:id])
end
def not_found
# renders app/reviews/not_found.html.erb
render :not_found,
status: :not_found
end
end
Note that this should be done in different view. If you add a <% if #review.present? %> to your reviews/show.html.erb view you should get your Rails licence revoked as the views one and only job is to display the review.
You can also configure the responses on the application level with config.exceptions_app.

Answer 2

The problem is that if the ID does not correspond to a review in the database, the #review object will be nil, and your line if #review.valid? will throw an error.
You need a different test, something like
<% if #review.present? %>
<div class='review-header'>
....
</div>
<% else %>
Review does not exist.
<% end %>