In Files

  • rexml/element.rb

REXML::Element

Represents a tagged XML element. Elements are characterized by having children, attributes, and names, and can themselves be children.

Constants

UNDEFINED

Attributes

attributes[R]

Mechanisms for accessing attributes and child elements of this element.

context[RW]

The context holds information about the processing environment, such as whitespace handling.

elements[R]

Mechanisms for accessing attributes and child elements of this element.

Public Class Methods

new( arg = UNDEFINED, parent=nil, context=nil ) click to toggle source

Constructor

arg

if not supplied, will be set to the default value. If a String, the name of this object will be set to the argument. If an Element, the object will be shallowly cloned; name, attributes, and namespaces will be copied. Children will not be copied.

parent

if supplied, must be a Parent, and will be used as the parent of this object.

context

If supplied, must be a hash containing context items. Context items include:

  • :respect_whitespace the value of this is :all or an array of strings being the names of the elements to respect whitespace for. Defaults to :all.

  • :compress_whitespace the value can be :all or an array of strings being the names of the elements to ignore whitespace on. Overrides :respect_whitespace.

  • :ignore_whitespace_nodes the value can be :all or an array of strings being the names of the elements in which to ignore whitespace-only nodes. If this is set, Text nodes which contain only whitespace will not be added to the document tree.

  • :raw can be :all, or an array of strings being the names of the elements to process in raw mode. In raw mode, special characters in text is not converted to or from entities.

 
               # File rexml/element.rb, line 58
def initialize( arg = UNDEFINED, parent=nil, context=nil )
  super(parent)

  @elements = Elements.new(self)
  @attributes = Attributes.new(self)
  @context = context

  if arg.kind_of? String
    self.name = arg
  elsif arg.kind_of? Element
    self.name = arg.expanded_name
    arg.attributes.each_attribute{ |attribute|
      @attributes << Attribute.new( attribute )
    }
    @context = arg.context
  end
end
            

Public Instance Methods

add_attribute( key, value=nil ) click to toggle source

Adds an attribute to this element, overwriting any existing attribute by the same name.

key

can be either an Attribute or a String. If an Attribute, the attribute is added to the list of Element attributes. If String, the argument is used as the name of the new attribute, and the value parameter must be supplied.

value

Required if key is a String, and ignored if the first argument is an Attribute. This is a String, and is used as the value of the new Attribute. This should be the unnormalized value of the attribute (without entities).

Returns

the Attribute added

e = Element.new 'e'
e.add_attribute( 'a', 'b' )               #-> <e a='b'/>
e.add_attribute( 'x:a', 'c' )             #-> <e a='b' x:a='c'/>
e.add_attribute Attribute.new('b', 'd')   #-> <e a='b' x:a='c' b='d'/>
 
               # File rexml/element.rb, line 583
def add_attribute( key, value=nil )
  if key.kind_of? Attribute
    @attributes << key
  else
    @attributes[key] = value
  end
end
            
add_attributes(hash) click to toggle source

Add multiple attributes to this element.

hash

is either a hash, or array of arrays

el.add_attributes( {"name1"=>"value1", "name2"=>"value2"} )
el.add_attributes( [ ["name1","value1"], ["name2"=>"value2"] ] )
 
               # File rexml/element.rb, line 595
def add_attributes hash
  if hash.kind_of? Hash
    hash.each_pair {|key, value| @attributes[key] = value }
  elsif hash.kind_of? Array
    hash.each { |value| @attributes[ value[0] ] = value[1] }
  end
end
            
add_element(element, attrs=nil) click to toggle source

Adds a child to this element, optionally setting attributes in the element.

element

optional. If Element, the element is added. Otherwise, a new Element is constructed with the argument (see Element.initialize).

attrs

If supplied, must be a Hash containing String name,value pairs, which will be used to set the attributes of the new Element.

Returns

the Element that was added

el = doc.add_element 'my-tag'
el = doc.add_element 'my-tag', {'attr1'=>'val1', 'attr2'=>'val2'}
el = Element.new 'my-tag'
doc.add_element el
 
               # File rexml/element.rb, line 295
def add_element element, attrs=nil
  raise "First argument must be either an element name, or an Element object" if element.nil?
  el = @elements.add(element)
  attrs.each do |key, value|
    el.attributes[key]=Attribute.new(key,value,self)
  end       if attrs.kind_of? Hash
  el
end
            
add_namespace( prefix, uri=nil ) click to toggle source

Adds a namespace to this element.

prefix

the prefix string, or the namespace URI if uri is not supplied

uri

the namespace URI. May be nil, in which prefix is used as the URI

Evaluates to: this Element

a = Element.new("a")
a.add_namespace("xmlns:foo", "bar" )
a.add_namespace("foo", "bar")  # shorthand for previous line
a.add_namespace("twiddle")
puts a   #-> <a xmlns:foo='bar' xmlns='twiddle'/>
 
               # File rexml/element.rb, line 250
def add_namespace( prefix, uri=nil )
  unless uri
    @attributes["xmlns"] = prefix
  else
    prefix = "xmlns:#{prefix}" unless prefix =~ /^xmlns:/
    @attributes[ prefix ] = uri
  end
  self
end
            
add_text( text ) click to toggle source

A helper method to add a Text child. Actual Text instances can be added with regular Parent methods, such as add() and <<()

text

if a String, a new Text instance is created and added to the parent. If Text, the object is added directly.

Returns

this Element

e = Element.new('a')          #-> <e/>
e.add_text 'foo'              #-> <e>foo</e>
e.add_text Text.new(' bar')    #-> <e>foo bar</e>

Note that at the end of this example, the branch has 3 nodes; the ‘e’ element and 2 Text node children.

 
               # File rexml/element.rb, line 522
def add_text( text )
  if text.kind_of? String 
    if @children[-1].kind_of? Text
      @children[-1] << text
      return
    end
    text = Text.new( text, whitespace(), nil, raw() )
  end
  self << text unless text.nil?
  return self
end
            
attribute( name, namespace=nil ) click to toggle source

Attributes #

 
               # File rexml/element.rb, line 553
def attribute( name, namespace=nil )
  prefix = nil
  prefix = namespaces.index(namespace) if namespace
  prefix = nil if prefix == 'xmlns'
  attributes.get_attribute( "#{prefix ? prefix + ':' : ''}#{name}" )
end
            
cdatas() click to toggle source

Get an array of all CData children.

IMMUTABLE

 
               # File rexml/element.rb, line 627
def cdatas
  find_all { |child| child.kind_of? CData }.freeze
end
            
clone() click to toggle source

Creates a shallow copy of self.

d = Document.new "<a><b/><b/><c><d/></c></a>"
new_a = d.root.clone
puts new_a  # => "<a/>"
 
               # File rexml/element.rb, line 96
def clone
  self.class.new self
end
            
comments() click to toggle source

Get an array of all Comment children. IMMUTABLE

 
               # File rexml/element.rb, line 633
def comments
  find_all { |child| child.kind_of? Comment }.freeze
end
            
delete_attribute(key) click to toggle source

Removes an attribute

key

either an Attribute or a String. In either case, the attribute is found by matching the attribute name to the argument, and then removed. If no attribute is found, no action is taken.

Returns

the attribute removed, or nil if this Element did not contain a matching attribute

e = Element.new('E')
e.add_attribute( 'name', 'Sean' )             #-> <E name='Sean'/>
r = e.add_attribute( 'sur:name', 'Russell' )  #-> <E name='Sean' sur:name='Russell'/>
e.delete_attribute( 'name' )                  #-> <E sur:name='Russell'/>
e.delete_attribute( r )                       #-> <E/>
 
               # File rexml/element.rb, line 616
def delete_attribute(key)
  attr = @attributes.get_attribute(key)
  attr.remove unless attr.nil?
end
            
delete_element(element) click to toggle source

Deletes a child element.

element

Must be an Element, String, or Integer. If Element, the element is removed. If String, the element is found (via XPath) and removed. <em>This means that any parent can remove any descendant.<em> If Integer, the Element indexed by that number will be removed.

Returns

the element that was removed.

doc.delete_element "/a/b/c[@id='4']"
doc.delete_element doc.elements["//k"]
doc.delete_element 1
 
               # File rexml/element.rb, line 315
def delete_element element
  @elements.delete element
end
            
delete_namespace(namespace="xmlns") click to toggle source

Removes a namespace from this node. This only works if the namespace is actually declared in this node. If no argument is passed, deletes the default namespace.

Evaluates to: this element

doc = Document.new "<a xmlns:foo='bar' xmlns='twiddle'/>"
doc.root.delete_namespace
puts doc     # -> <a xmlns:foo='bar'/>
doc.root.delete_namespace 'foo'
puts doc     # -> <a/>
 
               # File rexml/element.rb, line 270
def delete_namespace namespace="xmlns"
  namespace = "xmlns:#{namespace}" unless namespace == 'xmlns'
  attribute = attributes.get_attribute(namespace)
  attribute.remove unless attribute.nil?
  self
end
            
document() click to toggle source

Evaluates to the document to which this element belongs, or nil if this element doesn’t belong to a document.

 
               # File rexml/element.rb, line 131
def document
  rt = root
  rt.parent if rt
end
            
each_element( xpath=nil ) click to toggle source

Synonym for #elements.each

 
               # File rexml/element.rb, line 392
def each_element( xpath=nil, &block ) # :yields: Element
  @elements.each( xpath, &block )
end
            
each_element_with_attribute( key, value=nil, max=0, name=nil ) click to toggle source

Iterates through the child elements, yielding for each Element that has a particular attribute set.

key

the name of the attribute to search for

value

the value of the attribute

max

(optional) causes this method to return after yielding for this number of matching children

name

(optional) if supplied, this is an XPath that filters the children to check.

doc = Document.new "<a><b @id='1'/><c @id='2'/><d @id='1'/><e/></a>"
# Yields b, c, d
doc.root.each_element_with_attribute( 'id' ) {|e| p e}
# Yields b, d
doc.root.each_element_with_attribute( 'id', '1' ) {|e| p e}
# Yields b
doc.root.each_element_with_attribute( 'id', '1', 1 ) {|e| p e}
# Yields d
doc.root.each_element_with_attribute( 'id', '1', 0, 'd' ) {|e| p e}
 
               # File rexml/element.rb, line 350
def each_element_with_attribute( key, value=nil, max=0, name=nil, &block ) # :yields: Element
  each_with_something( proc {|child| 
    if value.nil?
      child.attributes[key] != nil
    else
      child.attributes[key]==value
    end
  }, max, name, &block )
end
            
each_element_with_text( text=nil, max=0, name=nil ) click to toggle source

Iterates through the children, yielding for each Element that has a particular text set.

text

the text to search for. If nil, or not supplied, will itterate over all Element children that contain at least one Text node.

max

(optional) causes this method to return after yielding for this number of matching children

name

(optional) if supplied, this is an XPath that filters the children to check.

doc = Document.new '<a><b>b</b><c>b</c><d>d</d><e/></a>'
# Yields b, c, d
doc.each_element_with_text {|e|p e}
# Yields b, c
doc.each_element_with_text('b'){|e|p e}
# Yields b
doc.each_element_with_text('b', 1){|e|p e}
# Yields d
doc.each_element_with_text(nil, 0, 'd'){|e|p e}
 
               # File rexml/element.rb, line 381
def each_element_with_text( text=nil, max=0, name=nil, &block ) # :yields: Element
  each_with_something( proc {|child| 
    if text.nil?
      child.has_text?
    else
      child.text == text
    end
  }, max, name, &block )
end
            
get_elements( xpath ) click to toggle source

Synonym for Element.to_a This is a little slower than calling elements.each directly.

xpath

any XPath by which to search for elements in the tree

Returns

an array of Elements that match the supplied path

 
               # File rexml/element.rb, line 400
def get_elements( xpath )
  @elements.to_a( xpath )
end
            
get_text(path = nil) click to toggle source

Returns the first child Text node, if any, or nil otherwise. This method returns the actual Text node, rather than the String content.

doc = Document.new "<p>some text <b>this is bold!</b> more text</p>"
# The element 'p' has two text elements, "some text " and " more text".
doc.root.get_text.value            #-> "some text "
 
               # File rexml/element.rb, line 461
def get_text path = nil
  rv = nil
  if path
    element = @elements[ path ]
    rv = element.get_text unless element.nil?
  else
    rv = @children.find { |node| node.kind_of? Text }
  end
  return rv
end
            
has_attributes?() click to toggle source

Evaluates to true if this element has any attributes set, false otherwise.

 
               # File rexml/element.rb, line 562
def has_attributes?
  return !@attributes.empty?
end
            
has_elements?() click to toggle source

Evaluates to true if this element has at least one child Element

doc = Document.new "<a><b/><c>Text</c></a>"
doc.root.has_elements               # -> true
doc.elements["/a/b"].has_elements   # -> false
doc.elements["/a/c"].has_elements   # -> false
 
               # File rexml/element.rb, line 324
def has_elements?
  !@elements.empty?
end
            
has_text?() click to toggle source

Evaluates to true if this element has at least one Text child

 
               # File rexml/element.rb, line 432
def has_text?
  not text().nil?
end
            
ignore_whitespace_nodes() click to toggle source
 
               # File rexml/element.rb, line 161
def ignore_whitespace_nodes
  @ignore_whitespace_nodes = false
  if @context
    if @context[:ignore_whitespace_nodes]
      @ignore_whitespace_nodes = 
        (@context[:ignore_whitespace_nodes] == :all or
         @context[:ignore_whitespace_nodes].include? expanded_name)
    end
  end
end
            
inspect() click to toggle source
 
               # File rexml/element.rb, line 76
def inspect
  rv = "<#@expanded_name"

  @attributes.each_attribute do |attr|
    rv << " "
    attr.write( rv, 0 )
  end

  if children.size > 0
    rv << "> ... </>"
  else
    rv << "/>"
  end
end
            
instructions() click to toggle source

Get an array of all Instruction children. IMMUTABLE

 
               # File rexml/element.rb, line 639
def instructions
  find_all { |child| child.kind_of? Instruction }.freeze
end
            
namespace(prefix=nil) click to toggle source

Evalutas to the URI for a prefix, or the empty string if no such namespace is declared for this element. Evaluates recursively for ancestors. Returns the default namespace, if there is one.

prefix

the prefix to search for. If not supplied, returns the default namespace if one exists

Returns

the namespace URI as a String, or nil if no such namespace exists. If the namespace is undefined, returns an empty string

doc = Document.new("<a xmlns='1' xmlns:y='2'><b/><c xmlns:z='3'/></a>")
b = doc.elements['//b']
b.namespace           # -> '1'
b.namespace("y")      # -> '2'
 
               # File rexml/element.rb, line 222
def namespace(prefix=nil)
  if prefix.nil?
    prefix = prefix()
  end
  if prefix == ''
    prefix = "xmlns"
  else
    prefix = "xmlns:#{prefix}" unless prefix[0,5] == 'xmlns'
  end
  ns = attributes[ prefix ]
  ns = parent.namespace(prefix) if ns.nil? and parent
  ns = '' if ns.nil? and prefix == 'xmlns'
  return ns
end
            
namespaces() click to toggle source
 
               # File rexml/element.rb, line 202
def namespaces
  namespaces = {}
  namespaces = parent.namespaces if parent
  namespaces = namespaces.merge( attributes.namespaces )
  return namespaces
end
            
next_element() click to toggle source

Returns the next sibling that is an element, or nil if there is no Element sibling after this one

doc = Document.new '<a><b/>text<c/></a>'
doc.root.elements['b'].next_element          #-> <c/>
doc.root.elements['c'].next_element          #-> nil
 
               # File rexml/element.rb, line 409
def next_element
  element = next_sibling
  element = element.next_sibling until element.nil? or element.kind_of? Element 
  return element
end
            
node_type() click to toggle source
 
               # File rexml/element.rb, line 534
def node_type
  :element
end
            
prefixes() click to toggle source

Evaluates to an Array containing the prefixes (names) of all defined namespaces at this context node.

doc = Document.new("<a xmlns:x='1' xmlns:y='2'><b/><c xmlns:z='3'/></a>")
doc.elements['//b'].prefixes # -> ['x', 'y']
 
               # File rexml/element.rb, line 195
def prefixes
  prefixes = []
  prefixes = parent.prefixes if parent
  prefixes |= attributes.prefixes
  return prefixes
end
            
previous_element() click to toggle source

Returns the previous sibling that is an element, or nil if there is no Element sibling prior to this one

doc = Document.new '<a><b/>text<c/></a>'
doc.root.elements['c'].previous_element          #-> <b/>
doc.root.elements['b'].previous_element          #-> nil
 
               # File rexml/element.rb, line 420
def previous_element
  element = previous_sibling
  element = element.previous_sibling until element.nil? or element.kind_of? Element
  return element
end
            
raw() click to toggle source

Evaluates to true if raw mode is set for this element. This is the case if the context has :raw set to :all or an array containing the name of this element.

The evaluation is tested against expanded_name, and so is namespace sensitive.

 
               # File rexml/element.rb, line 178
def raw
  @raw = (@context and @context[:raw] and
          (@context[:raw] == :all or
           @context[:raw].include? expanded_name))
           @raw
end
            
root() click to toggle source
 
               # File rexml/element.rb, line 123
def root
  return elements[1] if self.kind_of? Document
  return self if parent.kind_of? Document or parent.nil?
  return parent.root
end
            
root_node() click to toggle source

Evaluates to the root node of the document that this element belongs to. If this element doesn’t belong to a document, but does belong to another Element, the parent’s root will be returned, until the earliest ancestor is found.

Note that this is not the same as the document element. In the following example, <a> is the document element, and the root node is the parent node of the document element. You may ask yourself why the root node is useful: consider the doctype and XML declaration, and any processing instructions before the document element… they are children of the root node, or siblings of the document element. The only time this isn’t true is when an Element is created that is not part of any Document. In this case, the ancestor that has no parent acts as the root node.

d = Document.new '<a><b><c/></b></a>'
a = d[1] ; c = a[1][1]
d.root_node == d   # TRUE
a.root_node        # namely, d
c.root_node        # again, d
 
               # File rexml/element.rb, line 119
def root_node
  parent.nil? ? self : parent.root_node
end
            
text( path = nil ) click to toggle source

A convenience method which returns the String value of the first child text element, if one exists, and nil otherwise.

Note that an element may have multiple Text elements, perhaps separated by other children. Be aware that this method only returns the first Text node.

This method returns the value of the first text child node, which ignores the raw setting, so always returns normalized text. See the Text::value documentation.

doc = Document.new "<p>some text <b>this is bold!</b> more text</p>"
# The element 'p' has two text elements, "some text " and " more text".
doc.root.text              #-> "some text "
 
               # File rexml/element.rb, line 450
def text( path = nil )
  rv = get_text(path)
  return rv.value unless rv.nil?
  nil
end
            
text=( text ) click to toggle source

Sets the first Text child of this object. See text() for a discussion about Text children.

If a Text child already exists, the child is replaced by this content. This means that Text content can be deleted by calling this method with a nil argument. In this case, the next Text child becomes the first Text child. In no case is the order of any siblings disturbed.

text

If a String, a new Text child is created and added to this Element as the first Text child. If Text, the text is set as the first Child element. If nil, then any existing first Text child is removed.

Returns

this Element.

doc = Document.new '<a><b/></a>'
doc.root.text = 'Sean'      #-> '<a><b/>Sean</a>'
doc.root.text = 'Elliott'   #-> '<a><b/>Elliott</a>'
doc.root.add_element 'c'    #-> '<a><b/>Elliott<c/></a>'
doc.root.text = 'Russell'   #-> '<a><b/>Russell<c/></a>'
doc.root.text = nil         #-> '<a><b/><c/></a>'
 
               # File rexml/element.rb, line 492
def text=( text )
  if text.kind_of? String
    text = Text.new( text, whitespace(), nil, raw() )
  elsif text and !text.kind_of? Text
    text = Text.new( text.to_s, whitespace(), nil, raw() )
  end
  old_text = get_text
  if text.nil?
    old_text.remove unless old_text.nil?
  else
    if old_text.nil?
      self << text
    else
      old_text.replace_with( text )
    end
  end
  return self
end
            
texts() click to toggle source

Get an array of all Text children. IMMUTABLE

 
               # File rexml/element.rb, line 645
def texts
  find_all { |child| child.kind_of? Text }.freeze
end
            
whitespace() click to toggle source

Evaluates to true if whitespace is respected for this element. This is the case if:

  1. Neither :respect_whitespace nor :compress_whitespace has any value

  2. The context has :respect_whitespace set to :all or an array containing the name of this element, and :compress_whitespace isn’t set to :all or an array containing the name of this element.

The evaluation is tested against expanded_name, and so is namespace sensitive.

 
               # File rexml/element.rb, line 145
def whitespace
  @whitespace = nil
  if @context
    if @context[:respect_whitespace]
      @whitespace = (@context[:respect_whitespace] == :all or
                     @context[:respect_whitespace].include? expanded_name)
    end
    @whitespace = false if (@context[:compress_whitespace] and
                            (@context[:compress_whitespace] == :all or
                             @context[:compress_whitespace].include? expanded_name)
                           )
  end
  @whitespace = true unless @whitespace == false
  @whitespace
end
            
write(writer=$stdout, indent=-1, transitive=false, ie_hack=false) click to toggle source

DEPRECATED

See REXML::Formatters

Writes out this element, and recursively, all children.

output

output an object which supports ‘<< string’; this is where the

document will be written.
indent

An integer. If -1, no indenting will be used; otherwise, the indentation will be this number of spaces, and children will be indented an additional amount. Defaults to -1

transitive

If transitive is true and indent is >= 0, then the output will be pretty-printed in such a way that the added whitespace does not affect the parse tree of the document

ie_hack

Internet Explorer is the worst piece of crap to have ever been written, with the possible exception of Windows itself. Since IE is unable to parse proper XML, we have to provide a hack to generate XML that IE’s limited abilities can handle. This hack inserts a space before the /> on empty tags. Defaults to false

out = ''
doc.write( out )     #-> doc is written to the string 'out'
doc.write( $stdout ) #-> doc written to the console
 
               # File rexml/element.rb, line 674
def write(writer=$stdout, indent=-1, transitive=false, ie_hack=false)
  Kernel.warn("#{self.class.name}.write is deprecated.  See REXML::Formatters")
  formatter = if indent > -1
      if transitive
        REXML::Formatters::Transitive.new( indent, ie_hack )
      else
        REXML::Formatters::Pretty.new( indent, ie_hack )
      end
    else
      REXML::Formatters::Default.new( ie_hack )
    end
  formatter.write( self, output )
end
            
xpath() click to toggle source
 
               # File rexml/element.rb, line 538
def xpath
  path_elements = []
  cur = self
  path_elements << __to_xpath_helper( self )
  while cur.parent
    cur = cur.parent
    path_elements << __to_xpath_helper( cur )
  end
  return path_elements.reverse.join( "/" )
end
            

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