std::bad_variant_access
| Defined in header <variant>
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||
| 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 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.
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 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 variants (function template) |
| (C++26) |
calls the provided functor with the argument held by the variant (public member function) |