Chapter 28. XmlValue

Chapter 28. XmlValue
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#include <DbXml.hpp>

class DbXml::XmlValue {
public:
	XmlValue();
	XmlValue(const std::string &value);
	XmlValue(const char *value);
	XmlValue(double value);
	XmlValue(bool value);
	XmlValue(const XmlDocument &document);
	XmlValue(Type type, const std::string &value);
    XmlValue(const std::string &typeURI, 
        const std::string &typeName, 
        const std::string &value);
	XmlValue(Type type, const XmlData &data);

	virtual ~XmlValue();
	XmlValue(const XmlValue &);
	XmlValue &operator=(const XmlValue &);
	bool operator==(const XmlValue &v) const
	bool equals(const XmlValue &v) const;
	bool isNull() const;
	...
};

The XmlValue class encapsulates the value of a node in an XML document. The type of the value may be any one of the enumerated types in the XmlValue::Type enumeration. There are convenience operators for specially handling the types of STRING, DOUBLE, and BOOLEAN, as well as a constructor to make an XmlValue from XmlDocument .

The XmlValue class provides several constructors, each of which maps a C++ type or Berkeley DB XML class onto an appropriate XmlValue type. The following table lists the constructor parameter mappings.

C++ Type	XmlValueType
No Parameter	NONE
std::string or const char *	STRING
double	DOUBLE
bool	BOOLEAN
XmlDocument	NODE
Type and std::string	String is converted to the specified type.
Type and XmlData	`XmlData` is converted to the specified type.

The Type may be any of of the following:

XmlValue::NONE	XmlValue::G_DAY
XmlValue::NODE	XmlValue::G_MONTH
XmlValue::ANY_SIMPLE_TYPE	XmlValue::G_MONTH_DAY
XmlValue::ANY_URI	XmlValue::G_YEAR
XmlValue::BASE_64_BINARY	XmlValue::G_YEAR_MONTH
XmlValue::BOOLEAN	XmlValue::HEX_BINARY
XmlValue::DATE	XmlValue::NOTATION
XmlValue::DATE_TIME	XmlValue::QNAME
XmlValue::DATE_TIME_DURATION	XmlValue::STRING
XmlValue::DECIMAL	XmlValue::TIME
XmlValue::DOUBLE	XmlValue::YEAR_MONTH_DURATION
XmlValue::DURATION	XmlValue::UNTYPE_ATOMIC
XmlValue::FLOAT	XmlValue::BINARY

The XmlValue class implements a set of methods that test if the XmlValue is of a named type. The XmlValue class also implements a set of methods that return the XmlValue as a value of a specified type. If the XmlValue is of type variable and no query context is provided when calling the test or cast methods, or no binding can be found for the variable, an exception is thrown.

In addition to type conversion, the XmlValue class also provides DOM-like navigation functions. Using these, you can retrieve features from the underlying document, such as the parent, an attribute, or a child of the current node.

This object is not thread-safe, and can only be safely used by one thread at a time in an application.

The following constructors are available for this class:

XmlValue(std:string &value)

XmlValue(const char *value)

Construct an XmlValue object of type STRING.

```
XmlValue(double value)
```
Construct an XmlValue object of type DOUBLE.
```
XmlValue(bool value)
```
Construct an XmlValue object of type BOOLEAN.
```
XmlValue(Type, std:string &value)
```
or
```
XmlValue(TYPE, const XmlData &value)
```
Construct an XmlValue object of the value Type, converting the string value to the specified type.
```
XmlValue(const std::string &typeURI, const std::string &typeName, 
    const std::string &value)
```
Construct an XmlValue object of the URI and type name provided, converting the string value to the specified type.
```
XmlValue(XmlDocument &document)
```
Construct an XmlValue object of type NODE.

XmlValue Methods

XmlValue Methods	Description
XmlValue::asBoolean	Return value as a boolean.
XmlValue::asDocument	Return value as XmlDocument.
XmlValue::asEventReader	Return value as XmlEventReader.
XmlValue::asNumber	Return value as a double.
XmlValue::asString	Return value as a string.
XmlValue::equals	Compare two XmlValue objects.
XmlValue::getAttributes	Get the node's attributes.
XmlValue::getFirstChild	Get the node's first child.
XmlValue::getLastChild	Get the node's last child.
XmlValue::getLocalName	Get the node's local name.
XmlValue::getNamespaceURI	Get the node's namespace URI.
XmlValue::getNextSibling	Get the node's next sibling node.
XmlValue::getNodeHandle	Return a string node handle for the value.
XmlValue::getNodeName	Get the name of the node value.
XmlValue::getNodeType	Get the node type of the node.
XmlValue::getNodeValue	Get the value of the node.
XmlValue::getOwnerElement	Get the node's owner element.
XmlValue::getParentNode	Get the node's parent node.
XmlValue::getPrefix	Get the node's namespace prefix.
XmlValue::getPreviousSibling	Get the node's previous sibling node.
XmlValue::getType	Get the type enumeration of the value.
XmlValue::getTypeName	Get the name of the type.
XmlValue::getTypeURI	Get the URI for the type.
XmlValue::isBinary	Check if value is binary.
XmlValue::isBoolean	Check if value is a boolean.
XmlValue::isNode	Check if value is node.
XmlValue::isNull	Check if the value is initialized.
XmlValue::isNumber	Check if value is a number .
XmlValue::isString	Check if value is a string .
XmlValue::isType	Check type of value.
XmlValue::operator==	Compare two XmlValue objects.