std:: bad_variant_access
|
Defined in header
<variant>
|
||
|
class
bad_variant_access
:
public
std::
exception
|
(since C++17) | |
std::bad_variant_access
is the type of the exception thrown in the following situations:
- std::get (std::variant) called with an index or type that does not match the currently active alternative.
- std::visit called to visit a variant that is valueless_by_exception .
Member functions
|
(constructor)
|
constructs a new
bad_variant_access
object
(public member function) |
|
operator=
|
replaces the
bad_variant_access
object
(public member function) |
|
what
|
returns the explanatory string
(public member function) |
std::bad_variant_access:: bad_variant_access
|
bad_variant_access
(
)
noexcept
;
|
(1) | (since C++17) |
|
bad_variant_access
(
const
bad_variant_access
&
other
)
noexcept
;
|
(2) | (since C++17) |
Constructs a new
bad_variant_access
object with an implementation-defined null-terminated byte string which is accessible through
what()
.
std::bad_variant_access
then
std::
strcmp
(
what
(
)
, other.
what
(
)
)
==
0
.
Parameters
| other | - | another exception object to copy |
std::bad_variant_access:: operator=
|
bad_variant_access
&
operator
=
(
const
bad_variant_access
&
other
)
noexcept
;
|
(since C++17) | |
Assigns the contents with those of
other
. If
*
this
and
other
both have dynamic type
std::bad_variant_access
then
std::
strcmp
(
what
(
)
, other.
what
(
)
)
==
0
after assignment.
Parameters
| other | - | another exception object to assign with |
Return value
* this
std::bad_variant_access:: what
|
virtual
const
char
*
what
(
)
const
noexcept
;
|
(since C++17) | |
Returns the explanatory string.
Parameters
(none)
Return value
Pointer to a null-terminated string with explanatory information. The string is suitable for conversion and display as a std::wstring . The pointer is guaranteed to be valid at least until the exception object from which it is obtained is destroyed, or until a non-const member function (e.g. copy assignment operator) on the exception object is called.
|
The returned string is encoded with the ordinary literal encoding during constant evaluation. |
(since C++26) |
Notes
Implementations are allowed but not required to override
what()
.
Inherited from std:: exception
Member functions
|
[virtual]
|
destroys the exception object
(virtual public member function of
std::exception
)
|
|
[virtual]
|
returns an explanatory string
(virtual public member function of
std::exception
)
|
Example
#include <iostream> #include <variant> int main() { std::variant<int, float> v; v = 12; try { std::get<float>(v); } catch (const std::bad_variant_access& e) { std::cout << e.what() << '\n'; } }
Possible output:
bad_variant_access
See also
|
(C++17)
|
reads the value of the variant given the index or the type (if the type is unique), throws on error
(function template) |
|
(C++17)
|
calls the provided functor with the arguments held by one or more
variant
s
(function template) |