Modifying DOM Tree

This topic explains how to create or modify a DOM tree by adding nodes and changing their contents.

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 TXmlEngElement class for a comprehensive list.

Figure 1. Creating a DOM tree

1. 
   Create an instance of RXmlEngDocument.

   RXmlEngDocument myDoc;

2. 
   Set the root node with the RXmlEngDocument::CreateDocumentElementL() function.

   _LIT8( KRootName, "playlist" );
   TXmlEngElement root = myDoc->CreateDocumentElementL( KRootName );

3. 
   Add child nodes and attributes by calling the TXmlEngElement::AddNewElementL() and TXmlEngElement::AddNewAttributeL() functions.

   _LIT8( KChildName, "song" );
   _LIT8( KAttrName, "filename" );
   
   for( TInt i=1;i<6;i++ ) 
       {
             TXmlEngElement tempElement = root.AddNewElementL( KChildName );
             TBuf8<12> value( _L8( "music0" ) );
             value.AppendNum( i );
             value.Append( _L8( ".mp3" ) );
             tempElement.AddNewAttributeL( KAttrName, value );
       }

4. 
   Swap the first two song elements by calling the TXmlEngElement::MoveAfterSibling() function.

   TXmlEngNode swap = root.FirstChild();
   swap.MoveAfterSibling( swap.NextSibling() );

5. 
   If you want to save the DOM tree into a file, call the XmlEnginePushL() method first. You must call the XmlEnginePushL() method before parsing or saving an XML file, and the XmlEnginePopAndClose() method after these operations.

 <playlist>
     <song filename = "music02.mp3"/>
     <song filename = "music01.mp3"/>
     <song filename = "music03.mp3"/>
     <song filename = "music04.mp3"/>
     <song filename = "music05.mp3"/>
 </playlist>