to_xml

Returns a string containing an XML representation of its receiver:

{'foo' => 1, 'bar' => 2}.to_xml
# =>
# <?xml version="1.0" encoding="UTF-8"?>
# <hash>
#   <foo type="integer">1</foo>
#   <bar type="integer">2</bar>
# </hash>

To do so, the method loops over the pairs and builds nodes that depend on the values. Given a pair key, value:

• If value is a hash there’s a recursive call with key as :root.

• If value is an array there’s a recursive call with key as :root, and key singularized as :children.

• If value is a callable object it must expect one or two arguments. Depending on the arity, the callable is invoked with the options hash as first argument with key as :root, and key singularized as second argument. The callable can add nodes by using options[:builder].

  'foo'.to_xml(lambda { |options, key| options[:builder].b(key) })
  # => "<b>foo</b>"
  

• If value responds to to_xml the method is invoked with key as :root.

  class Foo
    def to_xml(options)
      options[:builder].bar 'fooing!'
    end
  end
  
  { foo: Foo.new }.to_xml(skip_instruct: true)
  # => "<hash><bar>fooing!</bar></hash>"
  

• Otherwise, a node with key as tag is created with a string representation of value as text node. If value is nil an attribute “nil” set to “true” is added. Unless the option :skip_types exists and is true, an attribute “type” is added as well according to the following mapping:

  XML_TYPE_NAMES = {
    "Symbol"     => "symbol",
    "Fixnum"     => "integer",
    "Bignum"     => "integer",
    "BigDecimal" => "decimal",
    "Float"      => "float",
    "TrueClass"  => "boolean",
    "FalseClass" => "boolean",
    "Date"       => "date",
    "DateTime"   => "dateTime",
    "Time"       => "dateTime"
  }
  

By default the root node is “hash”, but that’s configurable via the :root option.

The default XML builder is a fresh instance of Builder::XmlMarkup. You can configure your own builder with the :builder option. The method also accepts options like :dasherize and friends, they are forwarded to the builder.