Reference object attribute in a nested model form

I’m confused about how to reference the attributes of a nested object in a form view.

I’m wanting to format the date in a specific way and when I try to get the attribute as I normally would, it’s giving me ‘doesn’t exist’ message.

So if the partial is named ‘_project_task’, i’m trying project_task.due_date. This isn’t working. Any help is appreciated.

For some reason it’s not that easy. It’s not seeing the attributes as a normal (what i call) ruby path (object.attribute).

f.project_task.start_date shows this error

undefined method `project_task' for #<ActionView::Helpers::FormBuilder:0x32e19b0>

project_task.start_date shows this

 undefined method `start_date' for nil:NilClass

f.start_date shows this

 undefined method `start_date' for #&lt;ActionView::Helpers::FormBuilder:0x2eda844&gt;

the f object is this class


I’ll take a look at the stackoverflow page, thanks.

You might be able to do something like the following:

<%= f.text_field :start_date, :class => "support_date", :value => f.project_task.start_date.to_s(:date_format) %>

Where :date_format is one of the following:

db            ‘%Y-%m-%d’   2008-08-20

long_ordinal     ‘&proc’      August 20th, 2008

long         ‘%B %e, %Y’  August 20, 2008

rfc822      ‘%e %b %Y’   20 Aug 2008

number     ‘%Y%m%d’     20080820

         short:‘%e %b’      20 Aug

You CAN define custom date formats for your app if you need to. (I would have to look it up as it has been awhile since I have done that.)

This thread on StackOverflow may be able to help as well.

Let us know if this works for you or not! :slight_smile:

I’m not sure that I am understanding exactly what you are trying to do…some code example of what you are trying to do would help me understand.

In a view you can format a date as such.


The (:long) tells Rails how to format the date.

However, I think you are wanting to do something with a form…so I’ll need more info so I can understand better!

I’ve tried formatting the default date in my environment.rb file, but it seems you have to use the .to_s method with that. What do you do in the case of formatting a text_field with a date in it?

well… problem KIND of solved. This doesn’t feel as clean as I would have hoped (or expect) from rails but basically I created 2 virtual attributes. start_date_string, due_date_string with getter and setter methods. I format the date like I want and voila. I need to come up with a better method name, but it’s working.

I’m not feeling like this is the best answer right now, but it’s working and when I learn more I can always come back.

The form and date partial are below. I’ve omitted non important fields/tags for brevity. So in the _project_task partial, instead of the date (on an edit action) being yyyy-mm-dd, which is rails default…*i want it to list as mm/dd/yyyy. So, with the solution to change the default rails format for the date, i still need to convert the value to a string. So i’m wondering how to access the attributes of the project_task object. BUT what i’m really wanting is to change the way rails displays the date in general so i don’t have to do anything with the actual variable…*all dates for the app just naturally display as mm/dd/yyyy.


<% f.fields_for :project_tasks do |builder| %>
	<%= error_messages_for :project_tasks %>
	<%= render "project_task", :f => builder %>
<% end %>


<div class="xsmall">
	<%= f.label :start_date, "start" %>
	<%= f.text_field :start_date, :class => "support_date", :value => project_task %>

Thanks for your help.