class Nokogiri::XML::Builder - nokogiri-1.6.3.1 Documentation

# 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

context[RW]

A context object for use when the block has no arguments

doc[RW]

The current Document object being built

parent[RW]

The parent of the current node being built

### Public Class Methods

new(options = {}) { |self| ... } click to toggle source

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

with(root, &block) click to toggle source

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

<<(string) click to toggle source

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

[](ns) click to toggle source

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

cdata(string) click to toggle source

Create a CDATA Node with content of `string`

    # File lib/nokogiri/xml/builder.rb, line 307
    def cdata string
      insert doc.create_cdata(string)
    end

comment(string) click to toggle source

Create a Comment Node with content of `string`

    # File lib/nokogiri/xml/builder.rb, line 313
    def comment string
      insert doc.create_comment(string)
    end

text(string) click to toggle source

Create a Text Node with content of `string`

    # File lib/nokogiri/xml/builder.rb, line 301
    def text string
      insert @doc.create_text_node(string)
    end

to_xml(*args) click to toggle source

Convert this Builder object to XML

    # File lib/nokogiri/xml/builder.rb, line 338
    def to_xml(*args)
      if Nokogiri.jruby?
        options = args.first.is_a?(Hash) ? args.shift : {}
        if !options[:save_with]
          options[:save_with] = Node::SaveOptions::AS_BUILDER
        end
        args.insert(0, options)
      end
      @doc.to_xml(*args)
    end

### Private Instance Methods

insert(node, &block) click to toggle source

Insert `node` as a child of the current Node

    # File lib/nokogiri/xml/builder.rb, line 382
    def insert(node, &block)
      node = @parent.add_child(node)
      if block_given?
        old_parent = @parent
        @parent    = node
        @arity ||= block.arity
        if @arity <= 0
          instance_eval(&block)
        else
          block.call(self)
        end
        @parent = old_parent
      end
      NodeBuilder.new(node, self)
    end