std::optional<T>::value
| constexpr T& value() &; constexpr const T & value() const &; |
(1) | (since C++17) |
| constexpr T&& value() &&; constexpr const T&& value() const &&; |
(2) | (since C++17) |
If *this contains a value, returns a reference to the contained value.
Otherwise, throws a std::bad_optional_access exception.
Parameters
(none)
Return value
A reference to the contained value.
Exceptions
std::bad_optional_access if *this does not contain a value.
Notes
The dereference operator operator*() does not check if this optional contains a value, which may be more efficient than value().
Example
Run this code
#include <optional> #include <iostream> int main() { std::optional<int> opt = {}; try { int n = opt.value(); } catch(const std::bad_optional_access& e) { std::cout << e.what() << '\n'; } }
Possible output:
bad optional access
See also
| returns the contained value if available, another value otherwise (public member function) | |
| accesses the contained value (public member function) | |
| (C++17) |
exception indicating checked access to an optional that doesn't contain a value (class) |