Dv::Sql::Object::ColumnRef Class Reference

A class that represents a reference to a column value in an Object. More...

#include <object.h>

Collaboration diagram for Dv::Sql::Object::ColumnRef:

Public Member Functions
template<typename T >
T	convert () const throw (std::logic_error)
	Obtain the associated column value as a value of type T.
template<typename T >
	operator T () const throw (std::logic_error)
	Obtain the associated column value as a value of type T.
template<typename T >
Object &	operator= (const T &t) throw (std::logic_error)
	Assign a new value to the referenced object column.
Object &	operator= (const ColumnRef &r) throw (std::logic_error)
	Copy one column value to another.
template<typename T >
bool	operator== (const T &t) const throw (std::logic_error)
	Check whether the column value referred to equals the parameter.
bool	operator== (const char *t) const throw (std::logic_error)
	Special case of check whether the column value referred to equals the parameter.
bool	operator== (const ColumnRef &r) throw (std::logic_error)
	Check whether the column value referred to equals the column value referred to by the parameter.
template<typename T >
bool	operator!= (const T &t) const throw (std::logic_error)
	Check whether the column value referred to is different from the parameter.
bool	operator!= (const char *t) const throw (std::logic_error)
	Special case of check whether the column value referred to is different from the parameter.
bool	operator!= (const ColumnRef &r) throw (std::logic_error)
	Check whether the column value referred to is different from the column value referred to by the parameter.
Object &	set_null (bool new_value)
	Set the corresponding value to null (or not).
bool	null () const
	Check null status of the underlying column value.
Object &	set_dirty (bool new_value)
	Set the dirty status of the underlying column value.
Object &	touch ()
	Set the dirty status of the underlying column value to true.
bool	dirty () const
	Check dirty status of the underlying column value.
Private Member Functions
	ColumnRef (Object &o, size_t i) throw (std::logic_error)
	Construcor.
Private Attributes
Object &	object_
	This ColumnRef refers to a column value in this object.
size_t	index_
	Index of column to which this ColumnRef refers (in `object_` ).
Friends
class	Object
template<typename T >
bool	operator!= (const T &t, const ColumnRef &c) throw (std::logic_error)
	Check whether the column value referred to by the second parameter is different from the first parameter.
template<typename T >
bool	operator== (const T &t, const ColumnRef &c) throw (std::logic_error)
	Check whether the column value referred to by the second parameter equals the first parameter.

Detailed Description

A class that represents a reference to a column value in an Object.

ColumnRef objects result from calling operator[] on an object. Such objects can convert to actual data values or be assigned to to change the value of a column in an object.

See also:: Object::operator[].

Definition at line 56 of file object.h.

Constructor & Destructor Documentation

Dv::Sql::Object::ColumnRef::ColumnRef	(	Object &	o,
		size_t	i
	)			throw (std::logic_error) `[private]`

Construcor.

Parameters:

	o	referenced object
	i	number of referenced column

Exceptions:

std::logic_error if i exceeds the arity of the object

See also:: Object::arity

Member Function Documentation

template<typename T >

T Dv::Sql::Object::ColumnRef::convert ( ) const throw (std::logic_error) [inline]

Obtain the associated column value as a value of type T.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 Dv::Util::Date birth_date = cust["birth_date"]; // will convert

Exceptions:

std::logic_error

if the conversion failed.

Definition at line 69 of file object.h.

References Dv::Sql::Object::data_, index_, and object_.

template<typename T >

Dv::Sql::Object::ColumnRef::operator T ( ) const throw (std::logic_error) [inline]

Obtain the associated column value as a value of type T.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 Dv::Util::Date birth_date = cust["birth_date"]; // will convert

Exceptions:

std::logic_error

if the conversion failed.

Definition at line 88 of file object.h.

template<typename T >

Object& Dv::Sql::Object::ColumnRef::operator= ( const T & t ) throw (std::logic_error) [inline]

Assign a new value to the referenced object column.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 cust["id"] = 123;

Parameters:

t

value to be assigned

Returns:: a reference to the underlying object

Exceptions:

std::logic_error

if the ColumnRef object refers to a nonexisting colum in the associated Object

Definition at line 105 of file object.h.

References index_, object_, and Dv::Sql::Object::set_data().

Object& Dv::Sql::Object::ColumnRef::operator= ( const ColumnRef & r ) throw (std::logic_error) [inline]

Copy one column value to another.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 Dv::Sql::Table::Ref account;
 Dv::Sql::Object acct(account);
 cust["id"] = acct["customer_id"]

Parameters:

r

the ColumnRef for which the associated column value is to be assigned to the column value associated with this ColumnRef

Returns:: a reference to the underlying Object of this ColumnRef

Exceptions:

std::logic_error

if this or ColumnRef object refers to a nonexisting colum in the associated Object

Definition at line 126 of file object.h.

References index_, object_, and Dv::Sql::Object::set_data().

template<typename T >

bool Dv::Sql::Object::ColumnRef::operator== ( const T & t ) const throw (std::logic_error) [inline]

Check whether the column value referred to equals the parameter.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 if ( cust["id"] == 123) {
   ..
 }

Parameters:

t

the value to compare with

Returns:: true iff the values are equal; false iff the values are not equal

Exceptions:

std::logic_error

if the conversion fails

Definition at line 146 of file object.h.

bool Dv::Sql::Object::ColumnRef::operator== ( const char * t ) const throw (std::logic_error) [inline]

Special case of check whether the column value referred to equals the parameter.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 if ( cust["name"] == "Jones") {
   ..
 }

Parameters:

t

the value to compare with

Returns:: true iff the values are equal; false iff the values are not equal

Exceptions:

std::logic_error

if the conversion fails

Definition at line 166 of file object.h.

bool Dv::Sql::Object::ColumnRef::operator== ( const ColumnRef & r ) throw (std::logic_error) [inline]

Check whether the column value referred to equals the column value referred to by the parameter.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 Dv::Sql::Table::Ref account;
 Dv::Sql::Object acct(account);
 if (cust["id"] == acct["customer_id"]) {
   ..
 }

Parameters:

r

the ColumnRef to compare with

Returns:: true iff the values are both null or are equal and (both) not null; false otherwise

Exceptions:

std::logic_error

if the conversion fails

Definition at line 187 of file object.h.

References Dv::Sql::Object::data_, index_, Dv::Sql::Object::null_, and object_.

template<typename T >

bool Dv::Sql::Object::ColumnRef::operator!= ( const T & t ) const throw (std::logic_error) [inline]

Check whether the column value referred to is different from the parameter.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 if ( cust["id"] != 123) {
   ..
 }

Parameters:

t

the value to compare with

Returns:: true iff the values are different; false iff the values are equal

Exceptions:

std::logic_error

if the conversion fails

Definition at line 210 of file object.h.

bool Dv::Sql::Object::ColumnRef::operator!= ( const char * t ) const throw (std::logic_error) [inline]

Special case of check whether the column value referred to is different from the parameter.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 if ( cust["name"] != "Jones") {
   ..
 }

Parameters:

t

the value to compare with

Returns:: true iff the values are different; false iff the values are equal

Exceptions:

std::logic_error

if the conversion fails

Definition at line 229 of file object.h.

bool Dv::Sql::Object::ColumnRef::operator!= ( const ColumnRef & r ) throw (std::logic_error) [inline]

Check whether the column value referred to is different from the column value referred to by the parameter.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 Dv::Sql::Table::Ref account;
 Dv::Sql::Object acct(account);
 if (cust["id"] != acct["customer_id"]) {
   ..
 }

Parameters:

r

the ColumnRef to compare with

Returns:: false iff the values are both null or are equal and (both) not null; true otherwise

Exceptions:

std::logic_error

if the conversion fails

Definition at line 250 of file object.h.

Object& Dv::Sql::Object::ColumnRef::set_null ( bool new_value )

Set the corresponding value to null (or not).

A null column corresponds to a database NULL value.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 cust["id"].set_null(true);

Parameters:

new_value

if true, the column value will be set to null, if false, it will be set to non-null.

Returns:: a reference to the referenced Object

bool Dv::Sql::Object::ColumnRef::null ( ) const

Check null status of the underlying column value.

A null column corresponds to a database NULL value.

Returns:: true iff the underlying column value is null

Object& Dv::Sql::Object::ColumnRef::set_dirty ( bool new_value )

Set the dirty status of the underlying column value.

A dirty column value represents the assumption that the value was not retrieved from the database, but was set explicitly by the user.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 cust["id"] = 123; 
 std::cout << cust.dirty("id"); // prints 1
 cust["id"].set_dirty(false);
 std::cout << cust.dirty("id"); // prints 0

Parameters:

new_value

if true, the dirty status will be set to true

Returns:: a reference to the referenced Object

Referenced by touch().

Object& Dv::Sql::Object::ColumnRef::touch ( ) [inline]

Set the dirty status of the underlying column value to true.

A dirty column value represents the assumption that the value was not retrieved from the database, but was set explicitly by the user.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 cust["id"].touch(); 
 std::cout << cust.dirty("id"); // prints 1

Returns:: a reference to the referenced Object

Definition at line 353 of file object.h.

References set_dirty().

bool Dv::Sql::Object::ColumnRef::dirty ( ) const

Check dirty status of the underlying column value.

A dirty column value represents the assumption that the value was not retrieved from the database, but was set explicitly by the user.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 cust["id"] = 123; 
 std::cout << cust.dirty("id"); // prints 1
 cust["id"].set_dirty(false);
 std::cout << cust.dirty("id"); // prints 0

Returns:: true iff the underlying column value is null

Friends And Related Function Documentation

friend class Object [friend]

Definition at line 57 of file object.h.

template<typename T >

bool operator!=	(	const T &	t,
		const ColumnRef &	c
	)			throw (std::logic_error) `[friend]`

Check whether the column value referred to by the second parameter is different from the first parameter.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 if ( 123 != cust["id"] ) {
   ..
 }

Parameters:

	t	the value to compare with
	c	the ColumnRef referring to the column value to compare `t` with

Returns:: true iff the values are different; false iff the values are equal

Exceptions:

std::logic_error

if the conversion fails

Definition at line 273 of file object.h.

template<typename T >

bool operator==	(	const T &	t,
		const ColumnRef &	c
	)			throw (std::logic_error) `[friend]`

Check whether the column value referred to by the second parameter equals the first parameter.

This is an ordinary function.

Example

 Dv::Sql::Table::Ref customer;
 Dv::Sql::Object cust(customer);
 if ( 123 == cust["id"] ) {
   ..
 }

Parameters:

	t	the value to compare with
	c	the ColumnRef referring to the column value to compare `t` with

Returns:: true iff the values are equal; false iff the values are not equal

Exceptions:

std::logic_error

if the conversion fails

Definition at line 295 of file object.h.

Member Data Documentation

Object& Dv::Sql::Object::ColumnRef::object_ [private]

This ColumnRef refers to a column value in this object.

Definition at line 383 of file object.h.

Referenced by convert(), operator=(), and operator==().

size_t Dv::Sql::Object::ColumnRef::index_ [private]

Index of column to which this ColumnRef refers (in object_ ).

Definition at line 385 of file object.h.

Referenced by convert(), operator=(), and operator==().

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

object.h

Dv::Sql::Object::ColumnRef Class Reference

Public Member Functions

Private Member Functions

Private Attributes

Friends

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Friends And Related Function Documentation

Member Data Documentation