Rails: How to only allow User to apply to job only once? - ruby-on-rails

Question

I am creating a job board, and I don't want to allow the users the option to apply for the same job twice. How can I limit this?
app/views/jobs/job.html.erb
<% if applied_to_this_job? %>
<div class="alert" role="alert">You have already applied to this job!</div>
<% else %>
<%= link_to 'Apply', new_job_application_path(#job) %>
<% end %>
app/helpers/jobs_helper.rb
def applied_to_this_job?
JobApplication.exists? user_id: current_user.id
end
Obviously this doesn't work because it checks if this user has applied to any job. How Can I check to see if the current user has applied to the job being viewed.
Also, how can I limit this at the controller level so that the user can't go to job_application/new and get to the form.

Answer 1

You would use a before_filter in the controller action.
class JobsController < ActionController::Base
before_filter :has_applied?, only: [new, create]
....
private
def has_applied?
if JobApplication.where(user_id: :current_user.id, job_id: params[:job_id]).any?
redirect_to :index, alert: "You have already applied"
end
end
end
This would allow the user to visit /jobs/new and post the application to /jobs/create unless they have applied. If they have applied, they will be redirected to the index in the sample code.
Also as another answer has noted, it would be wise to pass in the job id as well. Updated sample code above to reflect.

Answer 2

You need to check and see if the JobApplication object is for this #job try:
JobApplication.where( user_id: current_user.id, job_id: #job.id ).exists?

Answer 3

Although what you've accepted will work, I think it's somewhat of a surface-level fix.
You'll be much better using validators to determine if the user can actually create another job application. This will protect against any problems with the business logic in your "front-end" views
Here's how I'd handle it:
--
Uniq
#app/models/user.rb
class User < ActiveRecord::Base
has_one :job_application
end
#app/models/job_application.rb
class JobApplication < ActiveRecord::Base
belongs_to :user
validates :user_id, uniquness: true
end
You may also wish to give your database a uniq index for your user_id column:
> $ rails g migration AddUniqueIndex
#config/db/add_unique_index.rb
class AddUniqueIndex < ActiveRecord::Migration
def change
add_index :job_applications, [:job_id, :user_id], unique: true
end
end
This will give you a highly efficient DB-level uniqueness index - meaning that if you try and add any more applications than is permitted, it will either fail silently, or come back with an error.
Controller
The structure of the controller would allow you to be less stringent about the accessibility of the job_application functionality:
#app/views/jobs/job.html.erb
<% if current_user.has_applied?(params[:job_id]) %>
<div class="alert" role="alert">You have already applied to this job!</div>
<% else %>
<%= link_to 'Apply', new_job_application_path(#job) %>
<% end %>
#app/models/user.rb
class User < ActiveRecord::Base
has_many :job_applications
def has_applied?(job_id)
job_applications.find job_id
end
end