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 | (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) |
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().
*this and other both have dynamic type std::bad_variant_access then std::strcmp(what(), other.what()) == 0.| other | - | another exception object to copy |
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.
| other | - | another exception object to assign with |
*this.
virtual const char* what() const noexcept; | (since C++17) |
Returns the explanatory string.
(none).
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.
Implementations are allowed but not required to override what().
|
[virtual] | destroys the exception object (virtual public member function of std::exception) |
|
[virtual] | returns an explanatory string (virtual public member function of std::exception) |
#include <variant>
#include <iostream>
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
|
(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) |
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https://en.cppreference.com/w/cpp/utility/variant/bad_variant_access