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Edit File: element.rdoc

== Class Element

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

- {Tasks for Parent}[parent_rdoc.html].
- {Tasks for Child}[child_rdoc.html].
- {Tasks for Node}[node_rdoc.html].
- {Module Enumerable}[https://docs.ruby-lang.org/en/master/Enumerable.html].

:include: ../tocs/element_toc.rdoc

=== New Element

==== Task: Create a Default Element

Use method
{Element::new}[../../../../REXML/Element.html#method-c-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}[../../../../REXML/Element.html#method-c-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}[../../../../REXML/Element.html#method-c-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}[../../../../REXML/Element.html#method-c-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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-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#[]}[../../../../REXML/Element.html#method-i-5B-5D]
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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-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?}[../../../../REXML/Element.html#method-i-has_attributes-3F]
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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-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?}[../../../../REXML/Element.html#method-i-has_elements-3F]
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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-next_element]
to retrieve the next element sibling:

d = REXML::Document.new '<a>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}[../../../../REXML/Element.html#method-i-previous_element]
to retrieve the previous element sibling:

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

Text Children

==== Task: Add a Text Node

Use method
{Element#add_text}[../../../../REXML/Element.html#method-i-add_text]
to add a text node to the element:

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

==== Task: Replace the First Text Node

Use method
{Element#text=}[../../../../REXML/Element.html#method-i-text-3D]
to replace the first text node in the element:

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

==== Task: Remove the First Text Node

Use method
{Element#text=}[../../../../REXML/Element.html#method-i-text-3D]
to remove the first text node in the element:

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

==== Task: Retrieve the First Text Node

Use method
{Element#get_text}[../../../../REXML/Element.html#method-i-get_text]
to retrieve the first text node in the element:

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

==== Task: Retrieve a Specific Text Node

Use method
{Element#get_text}[../../../../REXML/Element.html#method-i-get_text]
to retrieve the first text node in a specified element:

d = REXML::Document.new "<root>some text this is bold! 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?}[../../../../REXML/Element.html#method-i-has_text-3F]
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#[]}[../../../../REXML/Element.html#method-i-5B-5D]
to retrieve the child at a given index:

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

==== Task: Get All CDATA Children

Use method
{Element#cdatas}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-comments]
to retrieve all comment children:

xml_string = <<-EOT
 <root>
 
 
 </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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-texts]
to retrieve all text children:

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

=== Namespaces

==== Task: Add a Namespace

Use method
{Element#add_namespace}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-delete_namespace]
to remove a specific namespace from the element:

==== Task: Get a Namespace URI

Use method
{Element#namespace}[../../../../REXML/Element.html#method-i-namespace]
to retrieve a speficic namespace URI for the element:

xml_string = <<-EOT
 <root>
 <a xmlns='1' xmlns:y='2'>
 
 <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}[../../../../REXML/Element.html#method-i-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}[../../../../REXML/Element.html#method-i-prefixes]
to retrieve all prefixes (namespace names) for the element:

xml_string = <<-EOT
 <root>
 <a xmlns:x='1' xmlns:y='2'>
 
 <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}[../../../../REXML/Element.html#method-i-each_element]
to iterate over element children:

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

Output:

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

==== Task: Iterate Over Elements Having a Specified Attribute

Use method
{Element#each_element_with_attribute}[../../../../REXML/Element.html#method-i-each_element_with_attribute]
to iterate over element children that have a specified attribute:

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

Output:

==== Task: Iterate Over Elements Having a Specified Attribute and Value

Use method
{Element#each_element_with_attribute}[../../../../REXML/Element.html#method-i-each_element_with_attribute]
to iterate over element children that have a specified attribute and value:

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

Output:

==== Task: Iterate Over Elements Having Specified Text

Use method
{Element#each_element_with_text}[../../../../REXML/Element.html#method-i-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

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