std::optional<T>::operator->, std::optional<T>::operator*
constexpr const T* operator->() const; |
(1) | (since C++17) |
constexpr T* operator->(); |
(1) | (since C++17) |
constexpr const T& operator*() const&; |
(2) | (since C++17) |
constexpr T& operator*() &; |
(2) | (since C++17) |
constexpr const T&& operator*() const&&; |
(2) | (since C++17) |
constexpr T&& operator*() &&; |
(2) | (since C++17) |
Accesses the contained value.
1) Returns a pointer to the contained value.
2) Returns a reference to the contained value.
The behavior is undefined if *this does not contain a value.
Parameters
(none)
Return value
Pointer or reference to the contained value.
Exceptions
(none)
Notes
This operator does not check whether the optional contains a value! You can do so manually by using has_value() or simply operator bool(). Alternatively, if checked access is needed, value() or value_or() may be used.
Example
Run this code
#include <optional> #include <iostream> #include <string> int main() { using namespace std::string_literals; std::optional<int> opt1 = 1; std::cout<< "opt1: " << *opt1 << '\n'; *opt1 = 2; std::cout<< "opt1: " << *opt1 << '\n'; std::optional<std::string> opt2 = "abc"s; std::cout<< "opt2: " << *opt2 << " size: " << opt2->size() << '\n'; // You can "take" the contained value by calling operator* on a rvalue to optional auto taken = *std::move(opt2); std::cout << "taken: " << taken << " opt2: " << *opt2 << "size: " << opt2->size() << '\n'; }
Output:
opt1: 1 opt1: 2 opt2: abc size: 3 taken: abc opt2: size: 0
See also
returns the contained value (public member function) | |
returns the contained value if available, another value otherwise (public member function) |