LDK::XmlHandle Class Reference

#include <LDK/XML.h>

Collaboration diagram for LDK::XmlHandle:

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Public Member Functions
	XmlHandle (XmlNode *node)
	Create a handle from any node (at any depth of the tree.) This can be a null pointer.
	XmlHandle (const XmlHandle &ref)
	Copy constructor.
XmlHandle	operator= (const XmlHandle &ref)
XmlHandle	FirstChild () const
	Return a handle to the first child node.
XmlHandle	FirstChild (const char *value) const
	Return a handle to the first child node with the given name.
XmlHandle	FirstChildElement () const
	Return a handle to the first child element.
XmlHandle	FirstChildElement (const char *value) const
	Return a handle to the first child element with the given name.
XmlHandle	Child (const char *value, int index) const
XmlHandle	Child (int index) const
XmlHandle	ChildElement (const char *value, int index) const
XmlHandle	ChildElement (int index) const
XmlHandle	FirstChild (const String &_value) const
XmlHandle	FirstChildElement (const String &_value) const
XmlHandle	Child (const String &_value, int index) const
XmlHandle	ChildElement (const String &_value, int index) const
XmlNode *	Node () const
	Return the handle as a XmlNode. This may return null.
XmlElement *	Element () const
	Return the handle as a XmlElement. This may return null.
XmlText *	Text () const
	Return the handle as a XmlText. This may return null.
XmlUnknown *	Unknown () const
	Return the handle as a XmlUnknown. This may return null;.

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Detailed Description

A XmlHandle is a class that wraps a node pointer with null checks; this is an incredibly useful thing. Note that XmlHandle is not part of the TinyXml DOM structure. It is a separate utility class.

Take an example:

    <Document>
        <Element attributeA = "valueA">
            <Child attributeB = "value1" />
            <Child attributeB = "value2" />
        </Element>
    <Document>
    

Assuming you want the value of "attributeB" in the 2nd "Child" element, it's very easy to write a *lot* of code that looks like:

    XmlElement* root = document.FirstChildElement( "Document" );
    if ( root )
    {
        XmlElement* element = root->FirstChildElement( "Element" );
        if ( element )
        {
            XmlElement* child = element->FirstChildElement( "Child" );
            if ( child )
            {
                XmlElement* child2 = child->NextSiblingElement( "Child" );
                if ( child2 )
                {
                    // Finally do something useful.
    

And that doesn't even cover "else" cases. XmlHandle addresses the verbosity of such code. A XmlHandle checks for null pointers so it is perfectly safe and correct to use:

    XmlHandle docHandle( &document );
    XmlElement* child2 = docHandle.FirstChild( "Document" ).FirstChild( "Element" ).Child( "Child", 1 ).Element();
    if ( child2 )
    {
        // do something useful
    

Which is MUCH more concise and useful.

It is also safe to copy handles - internally they are nothing more than node pointers.

    XmlHandle handleCopy = handle;
    

What they should not be used for is iteration:

    int i=0;
    while ( true )
    {
        XmlElement* child = docHandle.FirstChild( "Document" ).FirstChild( "Element" ).Child( "Child", i ).Element();
        if ( !child )
            break;
        // do something
        ++i;
    }
    

It seems reasonable, but it is in fact two embedded while loops. The Child method is a linear walk to find the element, so this code would iterate much more than it needs to. Instead, prefer:

    XmlElement* child = docHandle.FirstChild( "Document" ).FirstChild( "Element" ).FirstChild( "Child" ).Element();

    for( child; child; child=child->NextSiblingElement() )
    {
        // do something
    }
    

Definition at line 1370 of file XML.h.

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Member Function Documentation

XmlHandle LDK::XmlHandle::Child	(	const char *	value,
		int	index
	)			const

Return a handle to the "index" child with the given name. The first child is 0, the second 1, etc.

XmlHandle LDK::XmlHandle::Child

(

int

index

)

const

Return a handle to the "index" child. The first child is 0, the second 1, etc.

XmlHandle LDK::XmlHandle::ChildElement	(	const char *	value,
		int	index
	)			const

Return a handle to the "index" child element with the given name. The first child element is 0, the second 1, etc. Note that only XmlElements are indexed: other types are not counted.

XmlHandle LDK::XmlHandle::ChildElement

(

int

index

)

const

Return a handle to the "index" child element. The first child element is 0, the second 1, etc. Note that only XmlElements are indexed: other types are not counted.

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The documentation for this class was generated from the following file:

• XML.h

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