Class Element

Class Element has methods from its superclasses and included modules; see:

• Tasks for Parent.

• Tasks for Child.

• Tasks for Node.

• Module Enumerable.

:include: ../tocs/element_toc.rdoc

New Element

Task: Create a Default Element

Use method Element::new with no arguments to create a default element:

e = REXML::Element.new
e.name    # => "UNDEFINED"
e.parent  # => nil
e.context # => nil

Task: Create a Named Element

Use method Element::new with a string name argument to create a named element:

e = REXML::Element.new('foo')
e.name    # => "foo"
e.parent  # => nil
e.context # => nil

Task: Create an Element with Name and Parent

Use method Element::new with name and parent arguments to create an element with name and parent:

p = REXML::Parent.new
e = REXML::Element.new('foo', p)
e.name    # => "foo"
e.parent  # => #<REXML::Parent @parent=nil, @children=[<foo/>]>
e.context # => nil

Task: Create an Element with Name, Parent, and Context

Use method Element::new with name, parent, and context arguments to create an element with name, parent, and context:

p = REXML::Parent.new
e = REXML::Element.new('foo', p, {compress_whitespace: :all})
e.name    # => "foo"
e.parent  # => #<REXML::Parent @parent=nil, @children=[<foo/>]>
e.context # => {:compress_whitespace=>:all}

Task: Create a Shallow Clone

Use method Element#clone to create a shallow clone of an element, copying only the name, attributes, and context:

e0 = REXML::Element.new('foo', nil, {compress_whitespace: :all})
e0.add_attribute(REXML::Attribute.new('bar', 'baz'))
e0.context = {compress_whitespace: :all}
e1 = e0.clone # => <foo bar='baz'/>
e1.name # => "foo"
e1.context # => {:compress_whitespace=>:all}

Attributes

Task: Create and Add an Attribute

Use method Element#add_attribute to create and add an attribute:

e = REXML::Element.new
e.add_attribute('attr', 'value') # => "value"
e['attr'] # => "value"
e.add_attribute('attr', 'VALUE') # => "VALUE"
e['attr'] # => "VALUE"

Task: Add an Existing Attribute

Use method Element#add_attribute to add an existing attribute:

e = REXML::Element.new
a = REXML::Attribute.new('attr', 'value')
e.add_attribute(a)
e['attr'] # => "value"
a = REXML::Attribute.new('attr', 'VALUE')
e.add_attribute(a)
e['attr'] # => "VALUE"

Task: Add Multiple Attributes from a Hash

Use method Element#add_attributes to add multiple attributes from a hash:

e = REXML::Element.new
h = {'foo' => 0, 'bar' => 1}
e.add_attributes(h)
e['foo'] # => "0"
e['bar'] # => "1"

Task: Add Multiple Attributes from an Array

Use method Element#add_attributes to add multiple attributes from an array:

e = REXML::Element.new
a = [['foo', 0], ['bar', 1]]
e.add_attributes(a)
e['foo'] # => "0"
e['bar'] # => "1"

Task: Retrieve the Value for an Attribute Name

Use method Element#[] to retrieve the value for an attribute name:

e = REXML::Element.new
e.add_attribute('attr', 'value') # => "value"
e['attr'] # => "value"

Task: Retrieve the Attribute Value for a Name and Namespace

Use method Element#attribute to retrieve the value for an attribute name:

xml_string = "<root xmlns:a='a' a:x='a:x' x='x'/>"
d = REXML::Document.new(xml_string)
e = d.root
e.attribute("x")      # => x='x'
e.attribute("x", "a") # => a:x='a:x'

Task: Delete an Attribute

Use method Element#delete_attribute to remove an attribute:

e = REXML::Element.new('foo')
e.add_attribute('bar', 'baz')
e.delete_attribute('bar')
e.delete_attribute('bar')
e['bar'] # => nil

Task: Determine Whether the Element Has Attributes

Use method Element#has_attributes? to determine whether the element has attributes:

e = REXML::Element.new('foo')
e.has_attributes? # => false
e.add_attribute('bar', 'baz')
e.has_attributes? # => true

Children

Element Children

Task: Create and Add an Element

Use method Element#add_element to create a new element and add it to this element:

e0 = REXML::Element.new('foo')
e0.add_element('bar')
e0.children # => [<bar/>]

Task: Add an Existing Element

Use method Element#add_element to add an element to this element:

e0 = REXML::Element.new('foo')
e1 = REXML::Element.new('bar')
e0.add_element(e1)
e0.children # => [<bar/>]

Task: Create and Add an Element with Attributes

Use method Element#add_element to create a new element with attributes, and add it to this element:

e0 = REXML::Element.new('foo')
e0.add_element('bar', {'name' => 'value'})
e0.children # => [<bar name='value'/>]

Task: Add an Existing Element with Added Attributes

Use method Element#add_element to add an element to this element:

e0 = REXML::Element.new('foo')
e1 = REXML::Element.new('bar')
e0.add_element(e1, {'name' => 'value'})
e0.children # => [<bar name='value'/>]

Task: Delete a Specified Element

Use method Element#delete_element to remove a specified element from this element:

e0 = REXML::Element.new('foo')
e1 = REXML::Element.new('bar')
e0.add_element(e1)
e0.children # => [<bar/>]
e0.delete_element(e1)
e0.children # => []

Task: Delete an Element by Index

Use method Element#delete_element to remove an element from this element by index:

e0 = REXML::Element.new('foo')
e1 = REXML::Element.new('bar')
e0.add_element(e1)
e0.children # => [<bar/>]
e0.delete_element(1)
e0.children # => []

Task: Delete an Element by XPath

Use method Element#delete_element to remove an element from this element by XPath:

e0 = REXML::Element.new('foo')
e1 = REXML::Element.new('bar')
e0.add_element(e1)
e0.children # => [<bar/>]
e0.delete_element('//bar/')
e0.children # => []

Task: Determine Whether Element Children

Use method Element#has_elements? to determine whether the element has element children:

e0 = REXML::Element.new('foo')
e0.has_elements? # => false
e0.add_element(REXML::Element.new('bar'))
e0.has_elements? # => true

Task: Get Element Descendants by XPath

Use method Element#get_elements to fetch all element descendant children by XPath:

xml_string = <<-EOT
<root>
  <a level='1'>
    <a level='2'/>
  </a>
</root>
EOT
d = REXML::Document.new(xml_string)
d.root.get_elements('//a') # => [<a level='1'> ... </>, <a level='2'/>]

Task: Get Next Element Sibling

Use method Element#next_element to retrieve the next element sibling:

d = REXML::Document.new '<a><b/>text<c/></a>'
d.root.elements['b'].next_element #-> <c/>
d.root.elements['c'].next_element #-> nil

Task: Get Previous Element Sibling

Use method Element#previous_element to retrieve the previous element sibling:

d = REXML::Document.new '<a><b/>text<c/></a>'
d.root.elements['c'].previous_element #-> <b/>
d.root.elements['b'].previous_element #-> nil

Text Children

Task: Add a Text Node

Use method Element#add_text to add a text node to the element:

d = REXML::Document.new('<a>foo<b/>bar</a>')
e = d.root
e.add_text(REXML::Text.new('baz'))
e.to_a # => ["foo", <b/>, "bar", "baz"]
e.add_text(REXML::Text.new('baz'))
e.to_a # => ["foo", <b/>, "bar", "baz", "baz"]

Task: Replace the First Text Node

Use method Element#text= to replace the first text node in the element:

d = REXML::Document.new('<root><a/>text<b/>more<c/></root>')
e = d.root
e.to_a # => [<a/>, "text", <b/>, "more", <c/>]
e.text = 'oops'
e.to_a # => [<a/>, "oops", <b/>, "more", <c/>]

Task: Remove the First Text Node

Use method Element#text= to remove the first text node in the element:

d = REXML::Document.new('<root><a/>text<b/>more<c/></root>')
e = d.root
e.to_a # => [<a/>, "text", <b/>, "more", <c/>]
e.text = nil
e.to_a # => [<a/>, <b/>, "more", <c/>]

Task: Retrieve the First Text Node

Use method Element#get_text to retrieve the first text node in the element:

d = REXML::Document.new('<root><a/>text<b/>more<c/></root>')
e = d.root
e.to_a # => [<a/>, "text", <b/>, "more", <c/>]
e.get_text # => "text"

Task: Retrieve a Specific Text Node

Use method Element#get_text to retrieve the first text node in a specified element:

d = REXML::Document.new "<root>some text <b>this is bold!</b> more text</root>"
e = d.root
e.get_text('//root') # => "some text "
e.get_text('//b')    # => "this is bold!"

Task: Determine Whether the Element has Text Nodes

Use method Element#has_text? to determine whethe the element has text:

e = REXML::Element.new('foo')
e.has_text? # => false
e.add_text('bar')
e.has_text? # => true

Other Children

Task: Get the Child at a Given Index

Use method Element#[] to retrieve the child at a given index:

d = REXML::Document.new '><root><a/>text<b/>more<c/></root>'
e = d.root
e[0] # => <a/>
e[1] # => "text"
e[2] # => <b/>

Task: Get All CDATA Children

Use method Element#cdatas to retrieve all CDATA children:

xml_string = <<-EOT
  <root>
    <![CDATA[foo]]>
    <![CDATA[bar]]>
  </root>
EOT
d = REXML::Document.new(xml_string)
d.root.cdatas # => ["foo", "bar"]

Task: Get All Comment Children

Use method Element#comments to retrieve all comment children:

xml_string = <<-EOT
  <root>
    <!--foo-->
    <!--bar-->
  </root>
EOT
d = REXML::Document.new(xml_string)
d.root.comments.map {|comment| comment.to_s } # => ["foo", "bar"]

Task: Get All Processing Instruction Children

Use method Element#instructions to retrieve all processing instruction children:

xml_string = <<-EOT
  <root>
    <?target0 foo?>
    <?target1 bar?>
  </root>
EOT
d = REXML::Document.new(xml_string)
instructions = d.root.instructions.map {|instruction| instruction.to_s }
instructions # => ["<?target0 foo?>", "<?target1 bar?>"]

Task: Get All Text Children

Use method Element#texts to retrieve all text children:

xml_string = '<root><a/>text<b/>more<c/></root>'
d = REXML::Document.new(xml_string)
d.root.texts # => ["text", "more"]

Namespaces

Task: Add a Namespace

Use method Element#add_namespace to add a namespace to the element:

e = REXML::Element.new('foo')
e.add_namespace('bar')
e.namespaces # => {"xmlns"=>"bar"}

Task: Delete the Default Namespace

Use method Element#delete_namespace to remove the default namespace from the element:

d = REXML::Document.new "<a xmlns:foo='bar' xmlns='twiddle'/>"
d.to_s # => "<a xmlns:foo='bar' xmlns='twiddle'/>"
d.root.delete_namespace # => <a xmlns:foo='bar'/>
d.to_s # => "<a xmlns:foo='bar'/>"

Task: Delete a Specific Namespace

Use method Element#delete_namespace to remove a specific namespace from the element:

d = REXML::Document.new "<a xmlns:foo='bar' xmlns='twiddle'/>"
d.to_s # => "<a xmlns:foo='bar' xmlns='twiddle'/>"
d.root.delete_namespace # => <a xmlns:foo='bar'/>
d.to_s # => "<a xmlns:foo='bar'/>"
d.root.delete_namespace('foo')
d.to_s # => "<a/>"

Task: Get a Namespace URI

Use method Element#namespace to retrieve a speficic namespace URI for the element:

xml_string = <<-EOT
  <root>
     <a xmlns='1' xmlns:y='2'>
       <b/>
       <c xmlns:z='3'/>
     </a>
  </root>
EOT
d = REXML::Document.new(xml_string)
b = d.elements['//b']
b.namespace      # => "1"
b.namespace('y') # => "2"

Task: Retrieve Namespaces

Use method Element#namespaces to retrieve all namespaces for the element:

xml_string = '<a xmlns="foo" xmlns:x="bar" xmlns:y="twee" z="glorp"/>'
d = REXML::Document.new(xml_string)
d.root.attributes.namespaces # => {"xmlns"=>"foo", "x"=>"bar", "y"=>"twee"}

Task: Retrieve Namespace Prefixes

Use method Element#prefixes to retrieve all prefixes (namespace names) for the element:

xml_string = <<-EOT
  <root>
     <a xmlns:x='1' xmlns:y='2'>
       <b/>
       <c xmlns:z='3'/>
     </a>
  </root>
EOT
d = REXML::Document.new(xml_string, {compress_whitespace: :all})
d.elements['//a'].prefixes # => ["x", "y"]
d.elements['//b'].prefixes # => ["x", "y"]
d.elements['//c'].prefixes # => ["x", "y", "z"]

Iteration

Task: Iterate Over Elements

Use method Element#each_element to iterate over element children:

d = REXML::Document.new '<a><b>b</b><c>b</c><d>d</d><e/></a>'
d.root.each_element {|e| p e }

Output:

<b> ... </>
<c> ... </>
<d> ... </>
<e/>

Task: Iterate Over Elements Having a Specified Attribute

Use method Element#each_element_with_attribute to iterate over element children that have a specified attribute:

d = REXML::Document.new '<a><b id="1"/><c id="2"/><d id="1"/><e/></a>'
a = d.root
a.each_element_with_attribute('id') {|e| p e }

Output:

<b id='1'/>
<c id='2'/>
<d id='1'/>

Task: Iterate Over Elements Having a Specified Attribute and Value

Use method Element#each_element_with_attribute to iterate over element children that have a specified attribute and value:

d = REXML::Document.new '<a><b id="1"/><c id="2"/><d id="1"/><e/></a>'
a = d.root
a.each_element_with_attribute('id', '1') {|e| p e }

Output:

<b id='1'/>
<d id='1'/>

Task: Iterate Over Elements Having Specified Text

Use method Element#each_element_with_text to iterate over element children that have specified text:

Context

#whitespace #ignore_whitespace_nodes #raw

Other Getters

#document #root #root_node #node_type #xpath #inspect