Consider the following test case:

class Foobar < ActiveRecord::Base
  validates_inclusion_of :foo_id, :in => 1..100   # this is a DB column
  attr_accessor :bar_id # this is not a DB column
  attr_accessor :foobar  # this is not a DB column
end

class FoobarController < ApplicationController
  # standard CRUD stuff, e.g. using resource_controller
end

<% form_for(@object) do |f| %> <%= f.select :foo_id, (1..102) %> <%= f.select :bar_id, (1..102) %> <%= f.text_field :foobar %> <% end %>

The problem

• Select any value in the first form.
• Select 102 in the second form so validation fails.
• The controller should re-render the form using the previously entered values.
• This works for foo_id and for :foobar, but not for bar_id if bar_id is not a string.

The cause

In ActionView::Helpers::FormOptionsHelper#option_value_selected? is decided whether a value is selected or not. This works for strings and arrays but NOT for numeric values contained in attr_accessor variables, because they are not type casted by ActiveRecord::Base.

If I put a line

RAILS_DEFAULT_LOGGER("selected=#{selected.inspect}, value=#{value.inspect}")

in lib/action_view/helpers/form_options_helper:441 (in option_value_selected?), for each option in the select field, it will echo something like

selected="1", value=1
selected="1", value=2
selected="1", value=3

and of course, these values are never equal because you cannot compare String and Integer.

Possible Solutions

I think it is safe to assume that since all values passed by a HTTP request are strings at first, a string comparison can be made by default. However adding a "value.to_s" to each comparison adds quite a hefty performance penalty (Rails profiler says about 30%) to every option line in a select field, so this is no solution.

The other way round would be more practicable - casting the "selected" property to a number if its #to_i method returns a positive number.

Please share your thoughts. How is typecasting done for methods representing AR::Base database columns? Is it possible to manually specify a data type for attr_accessor variables? Currently I do this manually in an after_initialize block in each model, which works, but is a little non-DRY.

Thank you,

Jens