DeleteSubtree (XmlDoc/XmlNode subroutine): Difference between revisions

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Revision as of 17:50, 22 January 2011

Delete selected subtree (XmlDoc and XmlNode classes)

DeleteSubtree is a member of the XmlDoc and XmlNode classes.

This subroutine deletes a subtree (a node and all of its attributes and all descendants of the node and their attributes) from an XmlDoc.

Syntax

nr:DeleteSubtree[( [xpath])] Throws XPathError

Syntax terms

nr An XmlDoc or XmlNode, used as the context node for the XPath expression. If an XmlDoc, the Root node is the context node.
XPath A Unicode string that is an XPath expression that results in a nodelist. The head of the nodelist is the "top" node of the subtree to delete. An optional argument, its default is a period (.), that is, the node referenced by the method object (nr). Prior to Sirius Mods version 7.6, this is an EBCDIC string.

Usage notes

  • Any pointers (as XmlNodes or in XmlNodelists) to any of the deleted nodes will subsequently evaluate to Null.
  • DeleteSubtree may not be used if the preceding and following siblings of the top of the subtree are both Text nodes, unless the AdjacentText property setting is Combine.
  • If the result of the argument XPath expression (XPath) is empty, DeleteSubtree returns without deleting any nodes.
  • If the top node in the deleted subtree was originally added to the document by an AddAttribute method with a URI argument which created a namespace declaration, DeleteSubtree applied to that node does not remove the namespace declaration. For example:
        %d = New
        %n = %d:AddElement('x')
        Print 'Before AddAttribute/Delete:' And %d:Serial(, 'EBCDIC')
        %n = %n:AddAttribute('p:a', 'v', 'ftp:a')
        %n:DeleteSubtree
        Print 'After  AddAttribute/Delete:' And %d:Serial(, 'EBCDIC')
    

    This results in:

        Before AddAttribute/Delete: <x/>
        After  AddAttribute/Delete: <x xmlns:p="ftp:a"/>
    
  • In the following circumstances, DeleteSubtree does not completely "undo" a preceding AddSubtree (or InsertSubtreeBefore) method:
    1. The top node in the deleted subtree is originally added to the document by an AddAttribute method and has a name prefix.
    2. This attribute node is copied (by AddSubtree or InsertSubtreeBefore) to a target where the attribute prefix is not in scope.
    3. The attribute node is removed by DeleteSubtree, but the namespace declaration for the prefix remains.

    For example:

        %d = New
        %n = %d:AddElement('x')
        %n2 = %n:AddElement('x1')
        %n = %n:AddElement('x2')
        %n2 = %n2:AddAttribute('p:a', 'v', 'ftp:a')
        Print 'Before AddSubtree/Delete:'
        Print %d:Serial(, 'EBCDIC')
        %n2 = %n:AddSubtree(%n2)
        %n2:DeleteSubtree
        Print 'After  AddSubtree/Delete:'
        Print %d:Serial(, 'EBCDIC')
    

    This results in:

        Before AddSubtree/Delete:
        <x><x1 xmlns:p="ftp:a" p:a="v"/><x2/></x>
        After  AddSubtree/Delete:
        <x><x1 xmlns:p="ftp:a" p:a="v"/><x2 xmlns:p="ftp:a"/></x>
    

Example

The method in the following example deletes the first employee child of the top-level Element of the XmlDoc:

    %doc:DeleteSubtree('/*/employee')

Request-Cancellation Errors

  • XPath is invalid.
  • Head of result of XPath is the Root node.
  • Head of result of XPath is a node whose left and right siblings are Text nodes, and the AdjacentText property setting is Disallow.
  • Element or Attribute within subtree has a prefix.
  • Insufficient free space exists in CCATEMP.

See Also

  • For more information about using XPath expressions, see XPath.