std::optional<T>::operator->, std::optional<T>::operator*
From cppreference.com
|
constexpr
const T* operator-
>
(
)
const
noexcept
;
|
(1) | (since C++17) |
|
constexpr T* operator-
>
(
)
noexcept
;
|
(1) | (since C++17) |
|
constexpr
const T& operator*
(
)
const
&
noexcept
;
|
(2) | (since C++17) |
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constexpr T& operator*
(
)
&
noexcept
;
|
(2) | (since C++17) |
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constexpr
const T&& operator*
(
)
const
&&
noexcept
;
|
(2) | (since C++17) |
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constexpr T&& operator*
(
)
&&
noexcept
;
|
(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.
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()
Example
Run this code
#include <iomanip> #include <iostream> #include <optional> #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: " << std::quoted(*opt2) << ", size: " << opt2->size() << '\n'; // You can "take" the contained value by calling operator* on an rvalue to optional auto taken = *std::move(opt2); std::cout << "taken: " << std::quoted(taken) << "\n" "opt2: " << std::quoted(*opt2) << ", size: " << opt2->size() << '\n'; }
Output:
opt1: 1 opt1: 2 opt2: "abc", size: 3 taken: "abc" opt2: "", size: 0
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 2762 | C++17 | operator-> and operator* might be potentially-throwing
|
made noexcept |
See also
| returns the contained value (public member function) |
|
| returns the contained value if available, another value otherwise (public member function) |