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#2606 ✓stale

form field values connected to attr_accessible values are not restored because of missing typecast

Reported by Jens | May 4th, 2009 @ 08:45 PM | in 3.x

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

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

<% form_for(@object) do |f| %> <%= :foo_id, (1..102) %> <%= :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,


Comments and changes to this ticket

  • Jeremy Kemper

    Jeremy Kemper May 4th, 2010 @ 06:48 PM

    • Milestone changed from 2.x to 3.x
  • Santiago Pastorino

    Santiago Pastorino February 2nd, 2011 @ 05:02 PM

    • State changed from “new” to “open”
    • Importance changed from “” to “”

    This issue has been automatically marked as stale because it has not been commented on for at least three months.

    The resources of the Rails core team are limited, and so we are asking for your help. If you can still reproduce this error on the 3-0-stable branch or on master, please reply with all of the information you have about it and add "[state:open]" to your comment. This will reopen the ticket for review. Likewise, if you feel that this is a very important feature for Rails to include, please reply with your explanation so we can consider it.

    Thank you for all your contributions, and we hope you will understand this step to focus our efforts where they are most helpful.

  • Santiago Pastorino

    Santiago Pastorino February 2nd, 2011 @ 05:02 PM

    • State changed from “open” to “stale”

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