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