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<task id="GUID-61056CE2-97BF-5D32-8AC5-E625FBC7D0EC" xml:lang="en"><title>Modifying
DOM Tree</title><shortdesc>This topic explains how to create or modify a DOM tree by adding
nodes and changing their contents. </shortdesc><prolog><metadata><keywords/></metadata></prolog><taskbody>
<prereq><p>Before you start, you must: </p> <ul>
<li id="GUID-AB0E481B-349C-5C60-ACB7-06EBA299E149"><p>understand the concept
of <xref href="http://www.w3.org/DOM/" scope="external">Document Object Model
(DOM)</xref>  </p> </li>
<li id="GUID-79A66EA2-4F81-57E9-A4DB-E64B5405B578"><p>understand the structure
and classes of the <xref href="GUID-5ACFA8E4-3C4B-5851-A43E-9FA72D0B8403.dita">XML
DOM Engine </xref> component </p> </li>
</ul> </prereq>
<context><p> </p> <p>The following diagram shows a sequence of calls that
create a DOM tree from an empty document. There are many functions in the
DOM Engine API that add nodes to a tree: refer to the reference documentation
of the <xref href="GUID-5748D958-9480-3358-A399-6B92293B86D9.dita"><apiname>TXmlEngElement</apiname></xref> class for a comprehensive
list. </p> <fig id="GUID-31E4FB65-7C28-513B-B8C0-5B057DC64A50">
<title>              Creating a DOM tree            </title>
<image href="GUID-3E0E2E54-CD8A-5BAF-A87B-BF51FD8890D6_d0e431356_href.png" placement="inline"/>
</fig> </context>
<steps id="GUID-DEA52036-E11C-5913-984B-663DD68D02DB">
<step id="GUID-E65A2FF6-2918-540B-97DB-C07500A6CB08"><cmd/>
<info>Create an instance of <xref href="GUID-5748D958-9480-3358-A399-6B92293B86D9.dita"><apiname>RXmlEngDocument</apiname></xref>. </info>
<stepxmp><codeblock id="GUID-B36F5C00-6974-54EC-939A-34BF05F5C04A" xml:space="preserve">RXmlEngDocument myDoc;</codeblock> </stepxmp>
</step>
<step id="GUID-858AD52F-0526-5DCC-B424-666D88F19E8E"><cmd/>
<info>Set the root node with the <xref href="GUID-5748D958-9480-3358-A399-6B92293B86D9.dita"><apiname>RXmlEngDocument::CreateDocumentElementL()</apiname></xref> function. </info>
<stepxmp><codeblock id="GUID-E890E160-294C-5218-B8A8-41EB7E7FE8A7" xml:space="preserve">_LIT8( KRootName, "playlist" );
TXmlEngElement root = myDoc-&gt;CreateDocumentElementL( KRootName );</codeblock> </stepxmp>
</step>
<step id="GUID-25D56F38-012F-5169-9925-07A6A7BBAC31"><cmd/>
<info>Add child nodes and attributes by calling the <xref href="GUID-5748D958-9480-3358-A399-6B92293B86D9.dita"><apiname>TXmlEngElement::AddNewElementL()</apiname></xref> and <xref href="GUID-5748D958-9480-3358-A399-6B92293B86D9.dita"><apiname>TXmlEngElement::AddNewAttributeL()</apiname></xref> functions. </info>
<stepxmp><codeblock id="GUID-5CCB071C-7042-5F07-A5DE-29C2D5CD01D6" xml:space="preserve">_LIT8( KChildName, "song" );
_LIT8( KAttrName, "filename" );

for( TInt i=1;i&lt;6;i++ ) 
    {
          TXmlEngElement tempElement = root.AddNewElementL( KChildName );
          TBuf8&lt;12&gt; value( _L8( "music0" ) );
          value.AppendNum( i );
          value.Append( _L8( ".mp3" ) );
          tempElement.AddNewAttributeL( KAttrName, value );
    }</codeblock> </stepxmp>
</step>
<step id="GUID-559B34A9-4A69-57E3-AF2A-D3E7F81728B0"><cmd/>
<info>Swap the first two song elements by calling the <xref href="GUID-5748D958-9480-3358-A399-6B92293B86D9.dita"><apiname>TXmlEngElement::MoveAfterSibling()</apiname></xref> function. </info>
<stepxmp><codeblock id="GUID-6B4EDCE6-A688-5A0E-B4D9-9CF2ABD8DE5F" xml:space="preserve">TXmlEngNode swap = root.FirstChild();
swap.MoveAfterSibling( swap.NextSibling() );</codeblock> </stepxmp>
</step>
<step id="GUID-D648ADF3-10A5-5FDC-BF2C-D08B095E5FE6"><cmd/>
<info>If you want to save the DOM tree into a file, call the <xref href="GUID-5748D958-9480-3358-A399-6B92293B86D9.dita"><apiname>XmlEnginePushL()</apiname></xref> method
first. </info>
<info>You must call the <xref href="GUID-5748D958-9480-3358-A399-6B92293B86D9.dita"><apiname>XmlEnginePushL()</apiname></xref> method
before parsing or saving an XML file, and the <xref href="GUID-5748D958-9480-3358-A399-6B92293B86D9.dita"><apiname>XmlEnginePopAndClose()</apiname></xref> method
after these operations. </info>
</step>
</steps>
<result><p>The result is a DOM tree corresponding to the following XML structure: </p> <codeblock id="GUID-E90DD401-DDA6-5A3F-9A26-8C5CBE6BE64E" xml:space="preserve">
 &lt;playlist&gt;
     &lt;song filename = "music02.mp3"/&gt;
     &lt;song filename = "music01.mp3"/&gt;
     &lt;song filename = "music03.mp3"/&gt;
     &lt;song filename = "music04.mp3"/&gt;
     &lt;song filename = "music05.mp3"/&gt;
 &lt;/playlist&gt;
</codeblock> </result>
</taskbody><related-links>
<link href="GUID-C5C30218-311C-58D9-A990-3F95642F7517.dita"><linktext>Parsing XML
DOM</linktext></link>
</related-links></task>