Nokogiri::XML::Builder
class Nokogiri::XML::Builder
Nokogiri builder can be used for building XML and HTML documents.
Synopsis:
builder = Nokogiri::XML::Builder.new do |xml| xml.root { xml.products { xml.widget { xml.id_ "10" xml.name "Awesome widget" } } } end puts builder.to_xml
Will output:
<?xml version="1.0"?> <root> <products> <widget> <id>10</id> <name>Awesome widget</name> </widget> </products> </root>
Builder scope
The builder allows two forms- When the builder is supplied with a block that has a parameter, the outside scope is maintained- This means you can access variables that are outside your builder- If you don't need outside scope, you can use the builder without the “xml” prefix like this:
builder = Nokogiri::XML::Builder.new do root { products { widget { id_ "10" name "Awesome widget" } } } end
Special Tags
The builder works by taking advantage of method_missing. Unfortunately some methods are defined in ruby that are difficult or dangerous to remove. You may want to create tags with the name “type”, “class”, and “id” for example. In that case, you can use an underscore to disambiguate your tag name from the method call.
Here is an example of using the underscore to disambiguate tag names from ruby methods:
@objects = [Object.new, Object.new, Object.new] builder = Nokogiri::XML::Builder.new do |xml| xml.root { xml.objects { @objects.each do |o| xml.object { xml.type_ o.type xml.class_ o.class.name xml.id_ o.id } end } } end puts builder.to_xml
The underscore may be used with any tag name, and the last underscore will just be removed. This code will output the following XML:
<?xml version="1.0"?> <root> <objects> <object> <type>Object</type> <class>Object</class> <id>48390</id> </object> <object> <type>Object</type> <class>Object</class> <id>48380</id> </object> <object> <type>Object</type> <class>Object</class> <id>48370</id> </object> </objects> </root>
Tag Attributes
Tag attributes may be supplied as method arguments. Here is our previous example, but using attributes rather than tags:
@objects = [Object.new, Object.new, Object.new] builder = Nokogiri::XML::Builder.new do |xml| xml.root { xml.objects { @objects.each do |o| xml.object(:type => o.type, :class => o.class, :id => o.id) end } } end puts builder.to_xml
Tag Attribute Short Cuts
A couple attribute short cuts are available when building tags. The short cuts are available by special method calls when building a tag.
This example builds an “object” tag with the class attribute “classy” and the id of “thing”:
builder = Nokogiri::XML::Builder.new do |xml| xml.root { xml.objects { xml.object.classy.thing! } } end puts builder.to_xml
Which will output:
<?xml version="1.0"?> <root> <objects> <object class="classy" id="thing"/> </objects> </root>
All other options are still supported with this syntax, including blocks and extra tag attributes.
Namespaces
Namespaces are added similarly to attributes. Nokogiri::XML::Builder assumes that when an attribute starts with “xmlns”, it is meant to be a namespace:
builder = Nokogiri::XML::Builder.new { |xml| xml.root('xmlns' => 'default', 'xmlns:foo' => 'bar') do xml.tenderlove end } puts builder.to_xml
Will output XML like this:
<?xml version="1.0"?> <root xmlns:foo="bar" xmlns="default"> <tenderlove/> </root>
Referencing declared namespaces
Tags that reference non-default namespaces (i.e. a tag “foo:bar”) can be built by using the #[] method.
For example:
builder = Nokogiri::XML::Builder.new do |xml| xml.root('xmlns:foo' => 'bar') { xml.objects { xml['foo'].object.classy.thing! } } end puts builder.to_xml
Will output this XML:
<?xml version="1.0"?> <root xmlns:foo="bar"> <objects> <foo:object class="classy" id="thing"/> </objects> </root>
Note the “foo:object” tag.
Document Types
To create a document type (DTD), access use the #doc method to get the current context document. Then call Nokogiri::XML::Node#create_internal_subset to create the DTD node.
For example, this Ruby:
builder = Nokogiri::XML::Builder.new do |xml| xml.doc.create_internal_subset( 'html', "-//W3C//DTD HTML 4.01 Transitional//EN", "http://www.w3.org/TR/html4/loose.dtd" ) xml.root do xml.foo end end puts builder.to_xml
Will output this xml:
<?xml version="1.0"?> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <root> <foo/> </root>
Attributes
A context object for use when the block has no arguments
The current Document object being built
The parent of the current node being built
Public Class Methods
Create a new Builder object- options
are sent to the top level Document that is being built.
Building a document with a particular encoding for example:
Nokogiri::XML::Builder.new(:encoding => 'UTF-8') do |xml| ... end
# File lib/nokogiri/xml/builder.rb, line 266 def initialize options = {}, root = nil, &block if root @doc = root.document @parent = root else namespace = self.class.name.split('::') namespace[-1] = 'Document' @doc = eval(namespace.join('::')).new @parent = @doc end @context = nil @arity = nil @ns = nil options.each do |k,v| @doc.send(:"#{k}=", v) end return unless block_given? @arity = block.arity if @arity <= 0 @context = eval('self', block.binding) instance_eval(&block) else yield self end @parent = @doc end
Create a builder with an existing root object. This is for use when you have an existing document that you would like to augment with builder methods. The builder context created will start with the given root
node.
For example:
doc = Nokogiri::XML(open('somedoc.xml')) Nokogiri::XML::Builder.with(doc.at('some_tag')) do |xml| # ... Use normal builder methods here ... xml.awesome # add the "awesome" tag below "some_tag" end
# File lib/nokogiri/xml/builder.rb, line 253 def self.with root, &block new({}, root, &block) end
Public Instance Methods
Append the given raw XML string
to the document
# File lib/nokogiri/xml/builder.rb, line 351 def << string @doc.fragment(string).children.each { |x| insert(x) } end
Build a tag that is associated with namespace ns
. Raises an ArgumentError if ns
has not been defined higher in the tree.
# File lib/nokogiri/xml/builder.rb, line 320 def [] ns if @parent != @doc @ns = @parent.namespace_definitions.find { |x| x.prefix == ns.to_s } end return self if @ns @parent.ancestors.each do |a| next if a == doc @ns = a.namespace_definitions.find { |x| x.prefix == ns.to_s } return self if @ns end @ns = { :pending => ns.to_s } return self end
© 2008–2016 Aaron Patterson, Mike Dalessio, Charles Nutter, Sergio Arbeo
Patrick Mahoney, Yoko Harada, Akinori Musha, John Shahid
Licensed under the MIT License.