A compiled XPath query object. More...

#include <xpathquery.h>

Public Member Functions
	XPathQuery (const Char8 query, XPathVariableSet variables=0)
	Construct a compiled object from XPath expression. More...

	~XPathQuery ()
	Destructor.

bool	EvaluateBoolean (const XPathNode &n) const
	Evaluate expression as boolean value in the specified context; performs Type conversion if necessary. More...

XPathNodeSet	EvaluateNodeSet (const XPathNode &n) const
	Evaluate expression as node set in the specified context. More...

double	EvaluateNumber (const XPathNode &n) const
	Evaluate expression as double value in the specified context; performs Type conversion if necessary. More...

String	EvaluateString (const XPathNode &n) const
	Evaluate expression as string value in the specified context; performs Type conversion if necessary. More...

size_t	EvaluateString (Char8 *buffer, size_t capacity, const XPathNode &n) const
	Evaluate expression as string value in the specified context; performs Type conversion if necessary. More...

	operator unspecified_bool_type () const
	Used to convert this to a boolean value in a safe way. More...

bool	operator! () const
	Logical not operator, used a workaround for borland compiler. More...

const XPathParseResult &	Result () const
	Get parsing Result (used to get compilation errors when XML_NO_EXCEPTIONS is enabled) More...

XPathValueType	ReturnType () const
	Get query expression return Type. More...

Detailed Description

A compiled XPath query object.

When you call XML::Node::FindNodes with an expression string as an argument, a query object is created behind the scenes. A query object represents a compiled XPath expression. Query objects can be needed in the following circumstances:

You can precompile expressions to query objects to save compilation time if it becomes an issue;
You can use query objects to evaluate XPath expressions which result in booleans, numbers or strings;
You can get the type of expression value via query object.

Query objects correspond to XML::XPathQuery type. They are immutable and non-copyable: they are bound to the expression at creation time and can not be cloned. If you want to put query objects in a container, allocate them on heap via new operator and store pointers to XML::XPathQuery in the container.

To evaluate an XPath expression there are a few EvaluatedType functions. According to XPath specification, value of any type can be converted to boolean, number or string value, but no type other than node set can be converted to node set. Because of this, XPathQuery::EvaluateBoolean(), XPathQuery::EvaluateNumber() and XPathQuery::EvaluateString() always return a result, but EvaluateNodeSet results in an error if the return type is not node set.

Definition at line 91 of file xpathquery.h.

Constructor & Destructor Documentation

Mezzanine::XML::XPathQuery::XPathQuery	(	const Char8 *	query,
		XPathVariableSet *	variables = `0`
	)

explicit

Construct a compiled object from XPath expression.

Parameters

query	The query in the form of a c-string style char_t array.
variables	Any extra data the query might need, passing a null pointer simply omits passing any arguments.

Exceptions

Throws XPathException on compilation errors.

Member Function Documentation

bool Mezzanine::XML::XPathQuery::EvaluateBoolean ( const XPathNode & n) const

Evaluate expression as boolean value in the specified context; performs Type conversion if necessary.

Returns: A bool result of evaluating the expression.

Exceptions

If	XML_NO_EXCEPTIONS is not defined (by default it is not defined), throws std::bad_alloc on out of memory errors.

Parameters

n	The XPathNode that will serve as the context for the query.

XPathNodeSet Mezzanine::XML::XPathQuery::EvaluateNodeSet ( const XPathNode & n) const

Evaluate expression as node set in the specified context.

Parameters

n	The XPathNode that with serve as the context for the query.

Returns: An XPathNodeSet.

double Mezzanine::XML::XPathQuery::EvaluateNumber ( const XPathNode & n) const

Evaluate expression as double value in the specified context; performs Type conversion if necessary.

Parameters

n	The XPathNode that will serve as the context for the query.

Exceptions

Throws std::bad_alloc on out of memory errors.

Returns: A result as a double from evaluating the expression.

String Mezzanine::XML::XPathQuery::EvaluateString ( const XPathNode & n) const

Evaluate expression as string value in the specified context; performs Type conversion if necessary.

Parameters

n	The XPathNode that will serve as the context for the query.

Exceptions

Throws std::bad_alloc on out of memory errors.

Returns: A result as a String from evaluating the expression.

size_t Mezzanine::XML::XPathQuery::EvaluateString	(	Char8 *	buffer,
		size_t	capacity,
		const XPathNode &	n
	)		const

Evaluate expression as string value in the specified context; performs Type conversion if necessary.

Parameters

buffer	The place to store the c-style Character array
capacity	At most capacity characters are written to the destination buffer.
n	The XPathNode that with serve as the context for the query.

Exceptions

std::bad_alloc on out of memory errors.

Returns: Full result size is returned (includes terminating zero).

Mezzanine::XML::XPathQuery::operator unspecified_bool_type ( ) const

Used to convert this to a boolean value in a safe way.

Returns: Returns true if the internal data is set and false otherwise.

bool Mezzanine::XML::XPathQuery::operator! ( ) const

Logical not operator, used a workaround for borland compiler.

Returns: A bool that is the opposite of evaluatig this as a bool normally.

const XPathParseResult& Mezzanine::XML::XPathQuery::Result ( ) const

Get parsing Result (used to get compilation errors when XML_NO_EXCEPTIONS is enabled)

Returns: A const reference to an XPathParseResult.

XPathValueType Mezzanine::XML::XPathQuery::ReturnType ( ) const

Get query expression return Type.

Returns: A XPathValueType.

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

/home/sqeaky/Code/Mezzanine/Mezzanine/src/XML/xpathquery.h

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation