Kolosek

This is a complete tutorial for creating join table in Ruby on Rails. It will show you how to:

• generate the model,
• address associations and
• join table model.

Also, it will show you how to write a form with multiple select boxes and how to handle it in the controller.

First, let's create join tables in Rails way, with the city and the cleaner as references.

rails g model Assignment city:references cleaner:references

This will create the migration:

create_assignments.rb

class CreateAssignments < ActiveRecord::Migration

  def change

   create_table :assignments do |t|

    t.references :city, index: true, foreign_key: true

    t.references :cleaner, index: true, foreign_key: true

    t.timestamps null: false

  end

 end

end

cleaner.rb

class Cleaner < ActiveRecord::Base

 has_many :assignments

 has_many :cities, through: :assignments

end

city.rb

class City < ActiveRecord::Base

 has_many :assignments

 has_many :cleaners, :through => :assignments

end

assignment.rb

class Assignment < ActiveRecord::Base

 belongs_to :city

 belongs_to :cleaner

end

cleaners_controller.rb

private

def cleaner_params

 params.require(:cleaner).permit(city_ids: [])

end

_form.html.erb Select multiple form

<%= form_for(@cleaner) do |f| %>

 <p>

  <%= f.label :cities %><br />

  <% for city in City.all %>

   <%= check_box_tag "cleaner[city_ids][]", city.id,

@cleaner.cities.include?(city) %>

   <%=h city.name %><br />

  <% end %>

 </p>

 <div class="actions">

  <%= f.submit %>

 </div>

<% end %>

Hope you find this post helpful!

Originally posted at kolosek.com.