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::visitcalled to visit a variant that isvalueless_by_exception
|
(since C++26) |
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
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.
Return value
Pointer to an implementation-defined null-terminated string with explanatory information. The string is suitable for conversion and display as a std::wstring
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 variants (function template) |
|
(C++26)
|
calls the provided functor with the argument held by the variant (public member function) |