Validating field's presence fails even though the field is not blank - ruby-on-rails

Question

I'm trying to fill out an array with values from checkboxes. It works just fine when creating a record, but fails validation when editing. The params look right, which is what really confuses me:
"record"=>{... "type_array"=>["accounting"], ...}
It looks the same as the params from creating a new record. The fields in New.html.erb and Edit.html.erb also use the same markup.
Edit.html.erb
<div class="field">
<%= f.label :type_array, "What type of record?" %><br />
<% ["accounting", "agriculture", "automotive"].each do |type| %>
<%= check_box_tag 'record[type_array][]', type, (true if #record.type_list.include? type),
:id => type %>
<%= label_tag type, type.titleize, :class => type %><br />
<% end %>
</div>
Parts of Record.rb
validates :type_array, :presence => true
attr_accessor :type_array
attr_accessible :type_array
before_validation :set_type_list
private
def set_type_list
self.type_list = type_array.join ',' if type_array.present?
end
Am I missing something? When I remove the type_array validation and fill out the form, it acts like type_array is empty. Somewhere along the line, it must be lost or something.
I appreciate any help.
(Sidenote: if anyone has a better way to do the list of checkboxes, let me know)

Answer 1

Delete the line attr_accessor :type_array.
This creates accessor methods to a new instance variable, not to the model attribute type_array, which means that #record.type_array now refers to that instance variable instead of the attribute.
You almost never use attr_accessor or it's siblings attr_reader and attr_writer in Rails because you want to deal with model attributes, not instance variables.
Edit: You're using type_array as a virtual attribute.
class Record < ActiveRecord::Base
validates :type_array, :presence => true
attr_accessible :type_array
def type_array=(val)
self.type_list = val.join ','
end
def type_array
self.type_list.split ','
end
def type_array_before_type_cast
type_array
end
end
For the reason why you need that last function definition, see this question.