如何使用Ruby和Builder :: XMLMarkup模板生成XML文件？

Question

As you all know, with Rails it is possible to use Builder::XMLMarkup templates to provide an http reponse in XML format instead of HTML (with the respond_to command). My problem is that I would like to use the Builder::XMLMarkup templating system not with Rails but with Ruby only (ie a standalone program that generates/outputs an XML file from an XML template). The question is then twofold:

1. How do I tell the Ruby program which is the template I want to use? and
2. How do I tell the Builder class which is the output XML file ?

There is already a similar answer to that in Stackoverflow ( How do I generate XML from XMLBuilder using a .xml.builder file? ), but I am afraid it is only valid for Rails.

Answer 1

Here's a simple example showing the basics:

require 'builder'

@received_data = {:books => [{ :author => "John Doe", :title => "Doeisms" }, { :author => "Jane Doe", :title => "Doeisms II" }]}
@output = ""
xml = Builder::XmlMarkup.new(:target => @output, :indent => 1)

xml.instruct!
xml.books do
  @received_data[:books].each do |book|
    xml.book do
      xml.title book[:title]
      xml.author book[:author]
    end
  end
end

The @output object will contain your xml markup:

<?xml version="1.0" encoding="UTF-8"?>
<books>
 <book>
  <title>Doeisms</title>
  <author>John Doe</author>
 </book>
 <book>
  <title>Doeisms II</title>
  <author>Jane Doe</author>
 </book>
</books>

The Builder docs at github.com provide more examples and links to more documentation.

To select a specific template, you could pass arguments to your program for this decision.

Anyway, I prefer to use libxml-ruby to parse and build XML documents, but that's a matter of taste.

Answer 2

I used Tilt to do (the first part of) this. It's really easy:

require 'builder'
require 'tilt'
template = Tilt.new('templates/foo.builder')
output = template.render

That will get you a string representation of your xml. At that point you can write it out to disk yourself.