pqxx::result::field Class Reference

Reference to a field in a result set. More...

#include <result.hxx>

Inheritance diagram for pqxx::result::field:

List of all members.

Public Types
typedef size_t	size_type
Public Member Functions
	field (const tuple &T, tuple::size_type C) throw ()
	Constructor.
bool	operator== (const field &) const
	Byte-by-byte comparison of two fields (all nulls are considered equal).
bool	operator!= (const field &rhs) const
	Byte-by-byte comparison (all nulls are considered equal).
const char *	c_str () const
	Read as plain C string.
const char *	name () const
	Column name.
oid	type () const
	Column type.
template<typename T>
bool	to (T &Obj) const
	Read value into Obj; or leave Obj untouched and return false if null.
template<typename T>
bool	operator>> (T &Obj) const
	Read value into Obj; or leave Obj untouched and return false if null.
template<typename T>
bool	to (T &Obj, const T &Default) const
	Read value into Obj; or use Default & return false if null.
template<typename T>
T	as (const T &Default) const
	Return value as object of given type, or Default if null.
template<typename T>
T	as () const
	Return value as object of given type, or throw exception if null.
bool	is_null () const
size_type	size () const throw ()
tuple::size_type	num () const
Protected Member Functions
const tuple::size_type	col () const throw ()
Protected Attributes
tuple	m_tup
tuple::size_type	m_col

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Detailed Description

Reference to a field in a result set.

A field represents one entry in a tuple. It represents an actual value in the result set, and can be converted to various types.

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Member Typedef Documentation

typedef size_t pqxx::result::field::size_type

Reimplemented in pqxx::result::const_fielditerator.

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Constructor & Destructor Documentation

pqxx::result::field::field (  const tuple &  T, tuple::size_type  C )  throw ()

Constructor. Create field as reference to a field in a result set. Parameters: T  Tuple that this field is part of. C  Column number of this field.

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Member Function Documentation

template<typename T> T pqxx::result::field::as (   )  const

Return value as object of given type, or throw exception if null.

template<typename T> T pqxx::result::field::as (  const T &  Default  )  const

Return value as object of given type, or Default if null. Note that unless the function is instantiated with an explicit template argument, the Default value's type also determines the result type.

const char* pqxx::result::field::c_str (   )  const

Read as plain C string. Since the field's data is stored internally in the form of a zero-terminated C string, this is the fastest way to read it. Use the to() or as() functions to convert the string to other types such as int, or to C++ strings.

const tuple::size_type pqxx::result::field::col (   )  const throw () [protected]

bool pqxx::result::field::is_null (   )  const

const char* pqxx::result::field::name (   )  const

Column name.

tuple::size_type pqxx::result::field::num (   )  const

bool pqxx::result::field::operator!= (  const field &  rhs  )  const

Byte-by-byte comparison (all nulls are considered equal). Warning: See operator== for important information about this operator

bool pqxx::result::field::operator== (  const field &   )  const

Byte-by-byte comparison of two fields (all nulls are considered equal). Warning: null handling is still open to discussion and change! Handling of null values differs from that in SQL where a comparison involving a null value yields null, so nulls are never considered equal to one another or even to themselves. Null handling also probably differs from the closest equivalent in C++, which is the NaN (Not-a-Number) value, a singularity comparable to SQL's null. This is because the builtin == operator demands that a == a. The usefulness of this operator is questionable. No interpretation whatsoever is imposed on the data; 0 and 0.0 are considered different, as are null vs. the empty string, or even different (but possibly equivalent and equally valid) encodings of the same Unicode character etc.

template<typename T> bool pqxx::result::field::operator>> (  T &  Obj  )  const

Read value into Obj; or leave Obj untouched and return false if null.

size_type pqxx::result::field::size (   )  const throw ()

template<typename T> bool pqxx::result::field::to (  T &  Obj, const T &  Default )  const

Read value into Obj; or use Default & return false if null.

template<typename T> bool pqxx::result::field::to (  T &  Obj  )  const

Read value into Obj; or leave Obj untouched and return false if null.

oid pqxx::result::field::type (   )  const

Column type.

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Member Data Documentation

tuple::size_type pqxx::result::field::m_col [protected]

tuple pqxx::result::field::m_tup [protected]

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

• result.hxx
• result.cxx

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