caf::error Class Reference

A serializable type for storing error codes with category and optional, human-readable context information. More...

#include <error.hpp>

Inheritance diagram for caf::error:

Public Member Functions
	error (none_t) noexcept
	error (error &&) noexcept=default
error &	operator= (error &&) noexcept=default
	error (const error &)
error &	operator= (const error &)
template<class Enum , class = std::enable_if_t<is_error_code_enum_v<Enum>>>
	error (Enum code)
template<class Enum , class = std::enable_if_t<is_error_code_enum_v<Enum>>>
	error (Enum code, message context)
template<class Enum >
	error (error_code< Enum > code)
template<class E >
error &	operator= (E error_value)
template<class E >
error &	operator= (error_code< E > code)
uint8_t	code () const noexcept
	Returns the category-specific error code, whereas 0 means "no error".
type_id_t	category () const noexcept
	Returns the ::type_id of the category for this error.
const message &	context () const noexcept
	Returns context information to this error.
	operator bool () const noexcept
	Returns *this != none.
bool	operator! () const noexcept
	Returns *this == none.
bool	empty () const noexcept
	Returns whether this error was default-constructed.
int	compare (const error &) const noexcept
int	compare (uint8_t code, type_id_t category) const noexcept
void	reset () noexcept
	Reverts this error to "not an error" as if calling *this = error{}.

Friends
template<class Inspector >
bool	inspect (Inspector &f, error &x)

Related Functions
(Note that these are not member functions.)
CAF_CORE_EXPORT std::string	to_string (const error &x)
template<class Enum >
std::enable_if_t< is_error_code_enum_v< Enum >, error >	make_error (Enum code)
template<class Enum , class T , class... Ts>
std::enable_if_t< is_error_code_enum_v< Enum >, error >	make_error (Enum code, T &&x, Ts &&... xs)
bool	operator== (const error &x, none_t)
bool	operator== (none_t, const error &x)
template<class Enum >
std::enable_if_t< is_error_code_enum_v< Enum >, bool >	operator== (const error &x, Enum y)
template<class Enum >
std::enable_if_t< is_error_code_enum_v< Enum >, bool >	operator== (Enum x, const error &y)
bool	operator!= (const error &x, none_t)
bool	operator!= (none_t, const error &x)
template<class Enum >
std::enable_if_t< is_error_code_enum_v< Enum >, bool >	operator!= (const error &x, Enum y)
template<class Enum >
std::enable_if_t< is_error_code_enum_v< Enum >, bool >	operator!= (Enum x, const error &y)

Detailed Description

A serializable type for storing error codes with category and optional, human-readable context information.

Unlike error handling classes from the C++ standard library, this type is serializable. It consists of an 8-bit code, a 64-bit atom constant, plus optionally a ::message to store additional information.

Why not <tt>std::error_code</tt> or <tt>std::error_condition</tt>?

First, the standard does not define the values for std::errc. This means serializing error conditions (which are meant to be portable) is not safe in a distributed setting unless all machines are running the same operating system and version of the C++ standard library.

Second, the standard library primitives, unlike exceptions, do not offer an API for attaching additional context to an error. The error handling API offered by the standard is meant to wrap C system calls in a (source code) portable way. In a distributed setting, an error may not occur locally. In this case, an error code and category alone is often not satisfactory information when signalling errors back to end users. The additional context also enables composition of errors by modifying the message details as needed.

Why is there no <tt>string()</tt> member function?

The C++ standard library uses category singletons and virtual dispatching to correlate error codes to descriptive strings. However, singletons are a poor choice when it comes to serialization. CAF uses type IDs and meta objects instead.

Member Function Documentation

category()

type_id_t caf::error::category ( ) const

noexcept

Returns the ::type_id of the category for this error.

Precondition

*this != none

code()

uint8_t caf::error::code ( ) const

noexcept

Returns the category-specific error code, whereas 0 means "no error".

Precondition

*this != none

context()

const message & caf::error::context ( ) const

noexcept

Returns context information to this error.

Precondition

*this != none

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

• libcaf_core/caf/error.hpp