etree::Nullable< T > Class Template Reference

Lightweight wrapper to add nullable semantics to another type. More...

#include <element.hpp>

Public Member Functions
	Nullable ()
	Construct an unset Nullable.
	Nullable (const T &val)
	Construct a set Nullable containing a value. More...
	Nullable (const Nullable< T > &val)
	Copy the value from another Nullable. More...
	Nullable (T &&val)
	C++11: construct a set Nullable by moving a value. More...
	~Nullable ()
	Destroy the contained value if this Nullable is set.
ETREE_EXPLICIT	operator bool () const
	Evaluate to true if this Nullable is set.
T &	operator* ()
	Return the contained value, or throw missing_value_error().
const T &	operator* () const
	Return the contained value, or throw missing_value_error().
const T *	operator-> () const
	Return the contained value, or throw missing_value_error().
Nullable< T > &	operator= (const Nullable< T > &other)
	Copy the instance and its contained value, if any.
bool	operator== (const Nullable< T > &other) const
	Return true if both nullables are empty, or both nullables contain the same value.
bool	operator== (const T &other) const
	Return true if both nullables are empty, or both nullables contain the same value.

Detailed Description

template<typename T>
class etree::Nullable< T >

Lightweight wrapper to add nullable semantics to another type.

This template is presently only implemented for the Element type, attempting to instantiate it with other types will fail.

Nullable objects can be implicitly converted to boolean to test whether their contents exists, and dereferenced to access the stored value, if any:

Nullable<Element> maybe = parent.child("foo");
if(maybe) {
    // Nullable contains a value. "*maybe" will dereference its value.
} else {
    // Nullable is empty. "*maybe" will throw an exception.
}

Constructor & Destructor Documentation

template<typename T>

etree::Nullable< T >::Nullable

(

const T &

val

)

Construct a set Nullable containing a value.

Parameters

val	Value to copy.

template<typename T>

etree::Nullable< T >::Nullable

(

const Nullable< T > &

val

)

Copy the value from another Nullable.

Parameters

val	Value to copy.

template<typename T>

etree::Nullable< T >::Nullable

(

T &&

val

)

C++11: construct a set Nullable by moving a value.

Parameters

val	Value to copy.

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

• element.hpp
• element.cpp