The document discusses using the XML Builder gem to generate XML in a legacy format when the default to_xml method does not meet needs. It shows how to create a presenter object to encapsulate the logic for building the XML, and use XML Builder in the view to generate the XML according to the legacy format, providing an alternative to to_xml for complex or custom XML generation needs.

1. Using REST and XML Builder for
legacy XML
Keith Pitty
http://keithpitty.com

2. REST is great for responding to different formats

3. class NewsItemsController < ApplicationController
def index
@news_items = NewsItem.all
respond_to do |format|
format.html # index.rhtml
format.xml { render :xml => @news_items.to_xml }
end
end
def show
@news_item = NewsItem.find(params[:id])
respond_to do |format|
format.html # show.rhtml
format.xml { render :xml => @news_item.to_xml }
end
end
end

4. @news_items.to_xml

5. # == Schema Information
#
# Table name: news_items
#
# id :integer(4) not null, primary key
# heading :string(255)
# author :string(255)
# body :text
# created_at :datetime
# updated_at :datetime
#
class NewsItem < ActiveRecord::Base
end

6. So it’s easy to provide XML via to_xml, right?

7. But what if a legacy XML format is imposed?

8. <?xml version=quot;1.0quot; encoding=quot;UTF-8quot;?>
<newsletter>
<summary>
<title>The Trinity Tribune</title>
<date>June 9th, 2009</date>
</summary>
<feature>
<article heading=quot;Railscamp 5 a Roaring Successquot; by=quot;Lachie Coxquot;>
Railscamp 5 started out so well. Saturday was awesome...
</article>
</feature>
<article heading=quot;Bivou.ac blows Heroku away!quot; by=quot;Martin Stannardquot;>
Move over Heroku, bivou.ac is here!
</article>
<article heading=quot;Bananas de jourquot; by=quot;Tim Lucasquot;>
Bon jour, campers! Wanna share some cool code?
</article>
</newsletter>

9. Use presenter object and Builder::XmlBuilder

10. class NewsletterController < ApplicationController
def show
@newsletter = Newsletter.new
respond_to do |format|
format.xml { render :action => quot;show.xml.builderquot;,
:layout => false }
end
end
end

11. remember the legacy xml format?

12. <?xml version=quot;1.0quot; encoding=quot;UTF-8quot;?>
<newsletter>
<summary>
<title>The Trinity Tribune</title>
<date>June 9th, 2009</date>
</summary>
<feature>
<article heading=quot;Railscamp 5 a Roaring Successquot; by=quot;Lachie Coxquot;>
Railscamp 5 started out so well. Saturday was awesome...
</article>
</feature>
<article heading=quot;Bivou.ac blows Heroku away!quot; by=quot;Martin Stannardquot;>
Move over Heroku, bivou.ac is here!
</article>
<article heading=quot;Bananas de jourquot; by=quot;Tim Lucasquot;>
Bon jour, campers! Wanna share some cool code?
</article>
</newsletter>

13. app/views/newsletters/show.xml.builder
contains Builder::XmlMarkup

14. xml.instruct!
xml.newsletter {
xml.summary {
xml.title quot;The Trinity Tribunequot;
xml.date quot;#{Date.today.to_formatted_s(:rfc822)}quot;
}
xml.feature {
@newsletter.feature_article(quot;headingquot; => feature_article.heading,
quot;byquot; => feature_article.author)
}
@newsletter.articles.each { |article|
xml.article(quot;headingquot; => article.heading,
quot;byquot; => article.author)
}
}

15. Presenter class

16. class Newsletter
attr_reader :articles, :feature_article
def initialize
@articles = NewsItem.all_except_for_feature
end
def feature_article
@feature_article = NewsItem.feature
end
# Potential for more useful methods here
end

17. this example is simple and contrived

18. hopefully you can imagine how this technique
could be useful in more complex examples

19. Summary
REST needs a bit of help sometimes
XML Builder useful for producing XML in legacy format
Presenter object can help encapsulate what is required in the XML
markup