error_category Class
Represents the abstract, common base for objects that describes a category of error codes.
Syntax
class error_category;
constexpr error_category() noexcept;
virtual ~error_category();
error_category(const error_category&) = delete
Remarks
Two predefined objects implement error_category: generic_category and system_category.
Members
Typedefs
| Name | Description |
|---|---|
| value_type | A type that represents the stored error code value. |
Functions
| Name | Description |
|---|---|
| default_error_condition | Stores the error code value for an error condition object. |
| equivalent | Returns a value that specifies whether error objects are equivalent. |
| generic_category | |
| message | Returns the name of the specified error code. |
| name | Returns the name of the category. |
| system_category |
Operators
| Name | Description |
|---|---|
| operator= | Assignment operator. |
| operator== | Tests for equality between error_category objects. |
| operator!= | Tests for inequality between error_category objects. |
| operator< | Tests if the error_category object is less than the error_category object passed in for comparison. |
default_error_condition
Stores the error code value for an error condition object.
virtual error_condition default_error_condition(int _Errval) const;
Parameters
_Errval
The error code value to store in the error_condition.
Return Value
Returns error_condition(_Errval, *this).
Remarks
equivalent
Returns a value that specifies whether error objects are equivalent.
virtual bool equivalent(value_type _Errval,
const error_condition& _Cond) const;
virtual bool equivalent(const error_code& _Code,
value_type _Errval) const;
Parameters
_Errval
The error code value to compare.
_Cond
The error_condition object to compare.
_Code
The error_code object to compare.
Return Value
true if the category and value are equal; otherwise, false.
Remarks
The first member function returns *this == _Cond.category() && _Cond.value() == _Errval.
The second member function returns *this == _Code.category() && _Code.value() == _Errval.
generic_category
const error_category& generic_category();
message
Returns the name of the specified error code.
virtual string message(error_code::value_type val) const = 0;
Parameters
val
The error code value to describe.
Return Value
Returns a descriptive name of the error code val for the category. If the error code is unrecognized, returns "unknown error".
Remarks
name
Returns the name of the category.
virtual const char *name() const = 0;
Return Value
Returns the name of the category as a null-terminated byte string.
operator=
error_category& operator=(const error_category&) = delete;
operator==
Tests for equality between error_category objects.
bool operator==(const error_category& right) const;
Parameters
right
The object to be tested for equality.
Return Value
true if the objects are equal; false if the objects aren't equal.
Remarks
This member operator returns this == &right.
operator!=
Tests for inequality between error_category objects.
bool operator!=(const error_category& right) const;
Parameters
right
The object to be tested for inequality.
Return Value
true if the error_category object isn't equal to the error_category object passed in right; otherwise false.
Remarks
The member operator returns (!*this == right).
operator<
Tests if the error_category object is less than the error_category object passed in for comparison.
bool operator<(const error_category& right) const;
Parameters
right
The error_category object to be compared.
Return Value
true if the error_category object is less than the error_category object passed in for comparison; Otherwise, false.
Remarks
The member operator returns this < &right.
system_category
const error_category& system_category();
value_type
A type that represents the stored error code value.
typedef int value_type;
Remarks
This type definition is a synonym for int.