How to show a serialized Array attribute for a Rails ActiveRecord Model in a form? - ruby-on-rails

Question

We're using the "serialize" feature of ActiveRecord in Rails like this:
class User < ActiveRecord::Base
serialize :favorite_colors, Array
....
end
So we can have
u = User.last
u.favorite_colors = [ 'blue', 'red', 'grey' ]
u.save!
So basically ActiveRecord is serializing the array above and stores it in one database field called favorite_colors.
My question is: How do you allow a user to enter his favorite colors in a form?
Do you use a series of textfields? And once they're entered, how do you show them in a form for him to edit?
This is a question related to Rails Form Helpers for serialized array attribute.
Thanks

Answer 1

If you want multi-select HTML field, try:
= form_for #user do |f|
= f.select :favorite_colors, %w[full colors list], {}, :multiple => true
If you're using simple_form gem, you can present the options as check boxes easily:
= simple_form_for #user do |f|
= f.input :favorite_colors, as: :check_boxes, collection: %w[full colors list]

Answer 2

I have solved this problem by 'flattening' the array in the view and
reconstituting the array in the controller.
Some changes are needed in the model too, see below.
class User < ActiveRecord::Base
serialize :favorite_colors, Array
def self.create_virtual_attributes (*args)
args.each do |method_name|
10.times do |key|
define_method "#{method_name}_#{key}" do
end
define_method "#{method_name}_#{key}=" do
end
end
end
end
create_virtual_attributes :favorite_colors
end
If you don't define methods like the above, Rails would complain about the form element's
names in the view, such as "favorite_colors_0" (see below).
In the view, I dynamically create 10 text fields, favorite_colors_0, favorite_colors_1, etc.
<% 10.times do |key| %>
<%= form.label :favorite_color %>
<%= form.text_field "favorite_colors_#{key}", :value => #user.favorite_colors[key] %>
<% end %>
In the controller, I have to merge the favorite_colors_* text fields into an array BEFORE calling
save or update_attributes:
unless params[:user].select{|k,v| k =~ /^favorite_colors_/}.empty?
params[:user][:favorite_colors] = params[:user].select{|k,v| k =~ /^favorite_colors_/}.values.reject{|v| v.empty?}
params[:user].reject! {|k,v| k=~ /^favorite_colors_/}
end
One thing I'm doing is to hard-code 10, which limits how many elements you can have in the favorite_colors array. In the form, it also outputs 10 text fields. We can change 10 to 100 easily. But we will still have a limit. Your suggestion on how to remove this limit is welcome.
Hope you find this post useful.

Answer 3

To allow access to AR attributes, you have to grant them like this:
class User < ActiveRecord::Base
serialize :favorite_colors, Array
attr_accessible :favorite_colors
....
end