field

Variant-like class that can represent of any of the allowed database types.

Synopsis

Defined in header <boost/mysql/field.hpp>

class field;

Member Functions

Name	Description
as_blob	Retrieves a reference to the underlying `blob` value or throws an exception.
as_date	Retrieves a reference to the underlying `date` value or throws an exception.
as_datetime	Retrieves a reference to the underlying `datetime` value or throws an exception.
as_double	Retrieves a reference to the underlying `double` value or throws an exception.
as_float	Retrieves a reference to the underlying `float` value or throws an exception.
as_int64	Retrieves a reference to the underlying `std::int64_t` value or throws an exception.
as_string	Retrieves a reference to the underlying `std::string` value or throws an exception.
as_time	Retrieves a reference to the underlying `time` value or throws an exception.
as_uint64	Retrieves a reference to the underlying `std::uint64_t` value or throws an exception.
field [constructor]	Constructs a `field` holding NULL. — Copy constructor. — Move constructor. — Constructs a `field` holding an `int64`. — Constructs a `field` holding an `uint64`. — Constructors from character types would incorrectly construct a `field` holding an integer, so they are not allowed. — Constructs a `field` holding a string. — Constructs a `field` holding a `blob`. — Constructs a `field` holding a `float`. — Constructs a `field` holding a `double`. — Constructs a `field` holding a `date`. — Constructs a `field` holding a `datetime`. — Constructs a `field` holding a `time`. — Constructs a `field` from a `field_view`.
get_blob	Retrieves a reference to the underlying `blob` value (unchecked access).
get_date	Retrieves a reference to the underlying `date` value (unchecked access).
get_datetime	Retrieves a reference to the underlying `datetime` value (unchecked access).
get_double	Retrieves a reference to the underlying `double` value (unchecked access).
get_float	Retrieves a reference to the underlying `float` value (unchecked access).
get_int64	Retrieves a reference to the underlying `std::int64_t` value (unchecked access).
get_string	Retrieves a reference to the underlying `std::string` value (unchecked access).
get_time	Retrieves a reference to the underlying `time` value (unchecked access).
get_uint64	Retrieves a reference to the underlying `std::uint64_t` value (unchecked access).
is_blob	Returns whether this `field` is holding a blob value.
is_date	Returns whether this `field` is holding a `date` value.
is_datetime	Returns whether this `field` is holding a `datetime` value.
is_double	Returns whether this `field` is holding a `double` value.
is_float	Returns whether this `field` is holding a `float` value.
is_int64	Returns whether this `field` is holding a `int64` value.
is_null	Returns whether this `field` is holding a `NULL` value.
is_string	Returns whether this `field` is holding a string value.
is_time	Returns whether this `field` is holding a `time` value.
is_uint64	Returns whether this `field` is holding a `uint64` value.
kind	Returns the type of the value this `field` is holding.
operator field_view	Constructs a `field_view` pointing to `*this`.
operator=	Copy assignment. — Move assignment. — Replaces `this` with a `NULL`, changing the kind to `null` and destroying any previous contents. — Replaces `this` with `v`, changing the kind to `int64` and destroying any previous contents. — Replaces `this` with `v`, changing the kind to `uint64` and destroying any previous contents. — Assignments from character types would incorrectly assign an integer, so they are not allowed. — Replaces `this` with `v`, changing the kind to `string` and destroying any previous contents. — Replaces `this` with `v`, changing the kind to `blob` and destroying any previous contents. — Replaces `this` with `v`, changing the kind to `float_` and destroying any previous contents. — Replaces `this` with `v`, changing the kind to `double` and destroying any previous contents. — Replaces `this` with `v`, changing the kind to `date` and destroying any previous contents. — Replaces `this` with `v`, changing the kind to `datetime` and destroying any previous contents. — Replaces `this` with `v`, changing the kind to `time` and destroying any previous contents. — Replaces `*this` with `v`, changing the kind to `v.kind()` and destroying any previous contents.
~field [destructor]	Destructor.

Related Non-member Functions

Name	Description
operator!=	Tests for inequality.
operator<<	Streams a `field`.
operator==	Tests for equality.

This is a regular variant-like class that can represent any of the types that MySQL allows. It has value semantics (as opposed to field_view). Instances of this class are not created by the library. They should be created by the user, when the reference semantics of field_view are not appropriate.

Like a variant, at any point, a field always contains a value of certain type. You can query the type using kind and the is_xxx functions like is_int64. Use as_xxx and get_xxx for checked and unchecked value access, respectively. You can mutate a field by calling the assignment operator, or using the lvalue references returned by as_xxx and get_xxx.

Convenience header <boost/mysql.hpp>

Boost C++ Libraries

field

Synopsis

Member Functions

Related Non-member Functions

Description