libpqxx  4.0.1
pqxx::prepare::invocation Class Reference

Helper class for passing parameters to, and executing, prepared statements. More...

#include <prepared_statement.hxx>

Public Member Functions

 invocation (transaction_base &, const std::string &statement)
result exec () const
 Execute!
bool exists () const
 Has a statement of this name been defined?
invocationoperator() ()
 Pass null parameter.
template<typename T >
invocationoperator() (const T &v)
 Pass parameter value.
invocationoperator() (const binarystring &v)
 Pass binary parameter value for a BYTEA field.
template<typename T >
invocationoperator() (const T &v, bool nonnull)
 Pass parameter value.
invocationoperator() (const binarystring &v, bool nonnull)
 Pass binary parameter value for a BYTEA field.
template<typename T >
invocationoperator() (T *v, bool nonnull=true)
 Pass C-style parameter string, or null if pointer is null.
invocationoperator() (const char *v, bool nonnull=true)
 Pass C-style string parameter, or null if pointer is null.

Detailed Description

Helper class for passing parameters to, and executing, prepared statements.

Constructor & Destructor Documentation

pqxx::prepare::invocation::invocation ( transaction_base home,
const std::string &  statement 
)

Member Function Documentation

pqxx::result pqxx::prepare::invocation::exec ( ) const
bool pqxx::prepare::invocation::exists ( ) const

Has a statement of this name been defined?

invocation& pqxx::prepare::invocation::operator() ( )

Pass null parameter.

template<typename T >
invocation& pqxx::prepare::invocation::operator() ( const T &  v)

Pass parameter value.

Parameters
vparameter value; will be represented as a string internally.
invocation& pqxx::prepare::invocation::operator() ( const binarystring v)

Pass binary parameter value for a BYTEA field.

Parameters
vbinary string; will be passed on directly in binary form.
template<typename T >
invocation& pqxx::prepare::invocation::operator() ( const T &  v,
bool  nonnull 
)

Pass parameter value.

Parameters
vparameter value (will be represented as a string internally).
nonnullreplaces value with null if set to false.
invocation& pqxx::prepare::invocation::operator() ( const binarystring v,
bool  nonnull 
)

Pass binary parameter value for a BYTEA field.

Parameters
vbinary string; will be passed on directly in binary form.
nonnulldetermines whether to pass a real value, or NULL.
template<typename T >
invocation& pqxx::prepare::invocation::operator() ( T *  v,
bool  nonnull = true 
)

Pass C-style parameter string, or null if pointer is null.

This version is for passing C-style strings; it's a template, so any pointer type that to_string accepts will do.

Warning
Be very careful with the special constant NULL! Since NULL in C++ is an int, not a pointer, a value of NULL would cause the wrong version of this template to be invoked. To all intents and purposes it would look like you were trying to pass a regular zero as an integer value, instead of a null string. This is not a problem with pointer variables that may happen to be NULL, since in that case the value's type is not subject to any confusion. So if you know at compile time that you want to pass a null value, use the zero-argument version of this operator; if you don't want to do that, at least add a second argument of false to make clear that you want a null, not a zero.
Parameters
vparameter value (will be represented as a C++ string internally)
nonnullreplaces value with null if set to false
invocation& pqxx::prepare::invocation::operator() ( const char *  v,
bool  nonnull = true 
)

Pass C-style string parameter, or null if pointer is null.

This duplicates the pointer-to-template-argument-type version of the operator, but helps compilers with less advanced template implementations disambiguate calls where C-style strings are passed.


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