implement grouped_collection_select not working

Question

I want dropdown in User sign up form which will set the user role which belongs to a department. Here is are models

class Department < ActiveRecord::Base
  has_many :roles

end

class Role < ActiveRecord::Base
  belongs_to :department
  has_many :users
end

class User < ActiveRecord::Base
  belongs_to :roles
end

And in the registration form i am trying this:

=form.grouped_collection_select(:user, :role_id, @departments, :roles, :title, :id,:title)

This produces error undefined method `merge' for :title:Symbol

Department and Role both models contain "title"

I don't know where i am lacking

Answer 1

Your code should work fine if you removed the form from form.grouped_collection_select

OR

If you really need it and the form is already referring to a user form builder then you can skip the first argument of :user passed to the grouped_collection_from method

Using any form builder to initiate a helper method like (select,collection, grouped_collection, ...etc) will automatically passes its object to the helper and the helper will expect arguments starting after the object parameter.

Check this SO question: collection_select method gives error in Rails 3.1.1