TiXmlHandle

class TiXmlHandle

A TiXmlHandle is a class that wraps a node pointer with null checks; this is an incredibly useful thing. Note that TiXmlHandle 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:

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

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

TiXmlHandle docHandle( &document );
TiXmlElement* child2 = docHandle.FirstChild( "Document" ).FirstChild( "Element" ).Child( "Child", 1 ).ToElement();
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.

TiXmlHandle handleCopy = handle;

What they should not be used for is iteration:

int i=0;
while ( true )
{
    TiXmlElement* child = docHandle.FirstChild( "Document" ).FirstChild( "Element" ).Child( "Child", i ).ToElement();
    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:

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

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

Inheritance diagram

Inheritance diagram of TiXmlHandle

TiXmlHandle Child(char const *value, int index) const
TiXmlHandle Child(int index) const
TiXmlHandle Child(std::string const &_value, int index) const

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

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

TiXmlHandle ChildElement(char const *value, int index) const
TiXmlHandle ChildElement(int index) const
TiXmlHandle ChildElement(std::string const &_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 TiXmlElements are indexed: other types are not counted.

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

TiXmlElement *Element(void) const

Deprecated: use ToElement().

Return the handle as a TiXmlElement. This may return null.

TiXmlHandle FirstChild(void) const
TiXmlHandle FirstChild(char const *value) const
TiXmlHandle FirstChild(std::string const &_value) const

/// Return a handle to the first child node.

/// Return a handle to the first child node with the given name.

TiXmlHandle FirstChildElement(void) const
TiXmlHandle FirstChildElement(char const *value) const
TiXmlHandle FirstChildElement(std::string const &_value) const

/// Return a handle to the first child element.

/// Return a handle to the first child element with the given name.

TiXmlNode *Node(void) const

Deprecated: use ToNode().

Return the handle as a TiXmlNode. This may return null.

TiXmlText *Text(void) const

Deprecated: use ToText()

Return the handle as a TiXmlText. This may return null.

TiXmlElement *ToElement(void) const

Return the handle as a TiXmlElement. This may return null.

TiXmlNode *ToNode(void) const

Return the handle as a TiXmlNode. This may return null.

TiXmlText *ToText(void) const

Return the handle as a TiXmlText. This may return null.

TiXmlUnknown *ToUnknown(void) const

Return the handle as a TiXmlUnknown. This may return null.

TiXmlUnknown *Unknown(void) const

Deprecated: use ToUnknown()

Return the handle as a TiXmlUnknown. This may return null.

TiXmlHandle(TiXmlNode *_node)
TiXmlHandle(TiXmlHandle const &ref)

/// Create a handle from any node (at any depth of the tree.) This can be a null pointer.

/// Copy constructor