error_category Class
The latest version of this topic can be found at error_category Class.
Represents the abstract, common base for objects that describes a category of error codes.
Syntax
class error_category;
Remarks
Two predefined objects implement error_category: generic_category and system_category.
TypeDefs
| value_type | A type that represents the stored error code value. |
Member Functions
| default_error_condition | Stores the error code value for an error condition object. |
| equivalent | Returns a value that specifies whether error objects are equivalent. |
| message | Returns the name of the specified error code. |
| name | Returns the name of the category. |
Operators
| 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. |
Requirements
Header: <system_error>
Namespace: std
error_category::default_error_condition
Stores the error code value for an error condition object.
virtual error_condition default_error_condition(int _Errval) const;
Parameters
| Parameter | Description |
|---|---|
_Errval |
The error code value to store in the error_condition. |
Return Value
Returns error_condition(_Errval, *this).
Remarks
error_category::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
| Parameter | Description |
|---|---|
_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.
error_category::message
Returns the name of the specified error code.
virtual string message(error_code::value_type val) const = 0;
Parameters
| Parameter | Description |
|---|---|
val |
The error code value to describe. |
Return Value
Returns a descriptive name of the error code val for the category.
Remarks
error_category::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.
Remarks
error_category::operator==
Tests for equality between error_category objects.
bool operator==(const error_category& right) const;
Parameters
| Parameter | Description |
|---|---|
right |
The object to be tested for equality. |
Return Value
true if the objects are equal; false if the objects are not equal.
Remarks
This member operator returns this == &right.
error_category::operator!=
Tests for inequality between error_category objects.
bool operator!=(const error_category& right) const;
Parameters
| Parameter | Description |
|---|---|
right |
The object to be tested for inequality. |
Return Value
true if the error_category object is not equal to the error_category object passed in right; otherwise false.
Remarks
The member operator returns (!*this == right).
error_category::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
| Parameter | Description |
|---|---|
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.
error_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.