Question

I have a form with two collection_select fields, the first one is an easy one, it just gets a model named courses, which shows the course name, and of course returns the id of the selected course, the second is the one Im having problems with, its a collection_select of the similar courses a course may have.

The courses model:

class Course < ActiveRecord::Base
  extend FriendlyId
  friendly_id :name, use: :slugged 
  attr_accessible :code, :credits, :name, :description, :active

  has_many :similars, dependent: :destroy
  has_many :similar_courses, through: :similars, source: :similar

end

The similar model:

class Similar < ActiveRecord::Base
  attr_accessible :course_id, :similar_id

  belongs_to :course
  belongs_to :similar, class_name: "Course"

  validates :similar_id, presence: true
  validates :course_id, presence: true

end

this is the homologate model, the thing with this model is that a course must be approved or rejected if one wants to transfer classes and stuff like that:

class Homologation < ActiveRecord::Base
  attr_accessible :homologate_by, :homologate_course, :student_id
  belongs_to :user
end

this is the form Im having problems with:

<%= form_for(@homologation) do |f| %>
      <%= render 'shared/error_messages', object: @homologation %>
      <%= f.label :homologate_course %>
      <%= f.collection_select :homologate_course, Course.find(:all), :id, :name, :prompt => "Select a Course" %>

      <%= f.label :homologate_by %>
      <%= f.collection_select :homologate_by, Similar.find(:all), :similar_id, :name, :prompt => "Select a Similar Course" %>
    <div class="form-actions">
      <%= f.submit "Create Homologation", class: "btn btn-large btn-primary" %>
    </div>
    <% end %>
  </div>

Im getting the following error

http://dpaste.com/hold/827744/

the Bartolleti thing is the name of the course I want to be able to show, and that of course is not a method, but I dont know Why Im getting the error, I want to be able to show the names of the similar courses given the first collection field course…

Thank you for your help!

Answer 1

From the doc of collection_select :

collection_select(object, method, collection, value_method, text_method, options = {}, html_options = {})

Then with your code you have Course.find(Similar.find_by_id(:similar_id)).name as the text_method, that is why you get this error message.

One solution could be to add a method on your Similar model to get the similar course name :

def similar_name
  similar.name
end

then you can use it as the text_method in your collection_select :

<%= f.collection_select :homologate_by, Similar.find(:all), :similar_id, :similar_name, :prompt => "Select a Similar Course" %>