Forum: Ruby on Rails Confused about to_xml() in ActiveRecord::Base subclass

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michael_teter (Guest)
on 2009-01-09 18:43
(Received via mailing list)
Since all my efforts to control how to_xml() is formatting dates has
failed, I'm now considering writing my own to_xml().  However, from
the limited examples I've found, I just don't understand how to
actually reference the columns for the records in my record set.

Here's a simplified view of my ActiveRecord object:

class Errors < ActiveRecord::Base
  set_table_name "legacy_errors"

  # legacy_errors has three columns: id, msg, error_date
  # Since the default to_xml is generating error_dates in the format
"Mon Nov 03 00:00:00 -0600 2008",
  #    and I cannot seem to force a different behavior, I want to
create my own to_xml.

  # Examples online show the following as how to override to_xml:
    def to_xml(options = {})
      options[:indent] ||= 2
      xml = options[:builder] ||= =>
      xml.instruct! unless options[:skip_instruct]
      # v v v
      xml.level_one do
        xml.tag!(:second_level, 'content')
      # ^ ^ ^

The code between the v and ^ markers is where the body of each XML
object is generated.  If I were generating by hand, I would do
something like this:
errors.each do |err|
  s << "<id>" << << "</id>"
  s << "<msg>" << err.msg << "</msg>"
  s << "<error_date>" << err.error_date.strftime("%Y-%m-%d") << "</

I'm not at all understanding how to do my thing within the v ^ section
of to_xml().

Any help is appreciated!

Rob B. (Guest)
on 2009-01-09 19:21
(Received via mailing list)
On Jan 9, 2009, at 11:42 AM, michael_teter wrote:
>  # legacy_errors has three columns: id, msg, error_date
>      xml.instruct! unless options[:skip_instruct]
> something like this:
> Any help is appreciated!
> Thanks.

that should be the encoding of a single Errors instance.

   xml.error do |x|

I think that you'd get a bunch of errors with:

   Errors.find(:all, :conditions => [...]).to_xml(:root => 'errors')

By default, I get output of attributes like this:
     <created-at type="datetime">2009-01-09T02:58:31Z</created-at>
     <id type="integer">110</id>
     <reference>From Anne</reference>
When I do #to_xml.  Notice the date format for the type="datetime".
What is the actual class of error_date?  Is it a Date or a DateTime or
a Time?


Rob B.
michael_teter (Guest)
on 2009-01-09 20:01
(Received via mailing list)

Thanks much for the good response.

To answer your question about the data type, it's "date" in Oracle.
When I use the default to_xml() (without suppressing types and the
dasherizer) it looks like this:
<error-date type=\"ActiveRecord::ConnectionAdapters::OracleColumn
\">Wed Nov 12 00:00:00 -0600 2008</error-date>

In fact, every element is listed as "OracleColumn".  I did try the
following to control my date presentation:
      proc = {|options| options[:builder].tag!
('error_date_x', options[:object].error_date.strftime("%Y-%m-%d"))}
      s = errs.to_xml(:dasherize => false, :skip_types => true, :procs
=> [proc])
That just blows up.
NoMethodError: You have a nil object when you didn't expect it!
The error occurred while evaluating nil.error_date

What's really odd is I've been using the default to_xml() for months
and receiving "YYYY-MM-DD" as my format.  Now suddenly I'm getting a
different format.  Perhaps I updated gems and got something new...

So now, if I cannot simply control the formatting of that one column,
I'll do my own to_xml() (following your example).

On Jan 9, 11:20 am, Rob B. <removed_email_address@domain.invalid>
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