Create XML markup easily. All (well, almost all) methods sent to an XmlMarkup object will be translated to the equivalent XML markup. Any method with a block will be treated as an XML markup tag with nested markup in the block.

Examples will demonstrate this easier than words. In the following, xmis an XmlMarkupobject.

xm.em("emphasized")             # => <em>emphasized</em>
xm.em { xmm.b("emp & bold") }   # => <em><b>emph &amp; bold</b></em>
xm.a("A Link", "href"=>"")
                                # => <a href="">A Link</a>
xm.div { br }                    # => <div><br/></div>"name"=>"compile", "option"=>"fast")
                                # => <target option="fast" name="compile"\>
                                # NOTE: order of attributes is not specified.
xm.instruct!                   # <?xml version="1.0" encoding="UTF-8"?>
xm.html {                      # <html>
  xm.head {                    #   <head>
    xm.title("History")        #     <title>History</title>
  }                            #   </head>
  xm.body {                    #   <body>
    xm.comment! "HI"           #     <! -- HI -->
    xm.h1("Header")            #     <h1>Header</h1>
    xm.p("paragraph")          #     <p>paragraph</p>
  }                            #   </body>
}                              # </html>


  • The order that attributes are inserted in markup tags is undefined.

  • Sometimes you wish to insert text without enclosing tags. Use the text!method to accomplish this.


    xm.div {                          # <div>
      xm.text! "line";          #   line<br/>
      xm.text! "another line"; xmbr   #    another line<br/>
    }                                 # </div>
  • The special XML characters <, >, and & are converted to &lt;, &gt; and &amp; automatically. Use the << operation to insert text without modification.

  • Sometimes tags use special characters not allowed in ruby identifiers. Use the tag!method to handle these cases.


    xml.tag!("SOAP:Envelope") { ... }

    will produce …

    <SOAP:Envelope> ... </SOAP:Envelope>"

    tag!will also take text and attribute arguments (after the tag name) like normal markup methods. (But see the next bullet item for a better way to handle XML namespaces).

  • Direct support for XML namespaces is now available. If the first argument to a tag call is a symbol, it will be joined to the tag to produce a namespace:tag combination. It is easier to show this than describe it.

    xml.SOAP :Envelope do ... end

    Just put a space before the colon in a namespace to produce the right form for builder (e.g. “ SOAP:Envelope” => “ xml.SOAP :Envelope ”)

  • XmlMarkup builds the markup in any object (called a target) that accepts the <<method. If no target is given, then XmlMarkup defaults to a string target.


    xm =
    result = xm.title("yada")
    # result is a string containing the markup.
    buffer = ""
    xm =
    # The markup is appended to buffer (using <<)
    xm =
    # The markup is written to STDOUT (using <<)
    xm =
    x2 =>xm)
    # Markup written to +x2+ will be send to +xm+.
  • Indentation is enabled by providing the number of spaces to indent for each level as a second argument to Initial indentation may be specified using a third parameter.


    xm =>2)
    # xm will produce nicely formatted and indented XML.
    xm =>2, :margin=>4)
    # xm will produce nicely formatted and indented XML with 2
    # spaces per indent and an over all indentation level of 4.
    builder =>$stdout, :indent=>2) { |b| b.first("Jim"); b.last("Weirich) }
    # prints:
    #     <name>
    #       <first>Jim</first>
    #       <last>Weirich</last>
    #     </name>
  • The instance_eval implementation which forces self to refer to the message receiver as self is now obsolete. We now use normal block calls to execute the markup block. This means that all markup methods must now be explicitly send to the xml builder. For instance, instead of

    xml.div { strong("text") }

    you need to write:

    xml.div { xml.strong("text") }

    Although more verbose, the subtle change in semantics within the block was found to be prone to error. To make this change a little less cumbersome, the markup block now gets the markup object sent as an argument, allowing you to use a shorter alias within the block.

    For example:

    xml_builder =
    xml_builder.div { |xml|
Class Public methods

Create an XML markup builder. Parameters are specified by an option hash.


Object receiving the markup. out must respond to the <<operator. The default is a plain string target.

:indent=> indentation

Number of spaces used for indentation. The default is no indentation and no line breaks.

:margin=> initial_indentation_level

Amount of initial indentation (specified in levels, not spaces).


The :escape_attrs option is no longer supported by builder (and will be quietly ignored). String attribute values are now automatically escaped. If you need unescaped attribute values (perhaps you are using entities in the attribute values), then give the value as a Symbol. This allows much finer control over escaping attribute values.

# File activesupport/lib/active_support/vendor/builder-2.1.2/builder/xmlmarkup.rb, line 185
def initialize(options={})
  indent = options[:indent] || 0
  margin = options[:margin] || 0
  super(indent, margin)
  @target = options[:target] || ""
Instance Public methods

Insert a CDATA section into the XML markup.

For example:

xml.cdata!("text to be included in cdata")
    #=> <![CDATA[text to be included in cdata]]>
# File activesupport/lib/active_support/vendor/builder-2.1.2/builder/xmlmarkup.rb, line 259
def cdata!(text)
  _ensure_no_block block_given?
  _special("<![CDATA[", "]]>", text, nil)
# File activesupport/lib/active_support/vendor/builder-2.1.2/builder/xmlmarkup.rb, line 197
def comment!(comment_text)
  _ensure_no_block block_given?
  _special("<!-- ", " -->", comment_text, nil)
declare!(inst, *args, &block)

Insert an XML declaration into the XML markup.

For example:

xml.declare! :ELEMENT, :blah, "yada"
    # => <!ELEMENT blah "yada">
# File activesupport/lib/active_support/vendor/builder-2.1.2/builder/xmlmarkup.rb, line 208
def declare!(inst, *args, &block)
  @target << "<!#{inst}"
  args.each do |arg|
    case arg
    when String
      @target << %Q{ "#{arg}"} # " WART
    when Symbol
      @target << " #{arg}"
  if block_given?
    @target << " ["
    @target << "]"
  @target << ">"
instruct!(directive_tag=:xml, attrs={})

Insert a processing instruction into the XML markup. E.g.

For example:

    #=> <?xml version="1.0" encoding="UTF-8"?>
xml.instruct! :aaa, :bbb=>"ccc"
    #=> <?aaa bbb="ccc"?>
# File activesupport/lib/active_support/vendor/builder-2.1.2/builder/xmlmarkup.rb, line 238
def instruct!(directive_tag=:xml, attrs={})
  _ensure_no_block block_given?
  if directive_tag == :xml
    a = { :version=>"1.0", :encoding=>"UTF-8" }
    attrs = a.merge attrs
  [:version, :encoding, :standalone])

Return the target of the builder.

# File activesupport/lib/active_support/vendor/builder-2.1.2/builder/xmlmarkup.rb, line 193
def target!