std::optional<T>::operator->, std::optional<T>::operator*

 

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std::optional

Member functions

optional::optional

optional::~optional

optional::operator=

Observers

optional::operator->optional::operator*

optional::operator booloptional::has_value

optional::value

optional::value_or

Iterators

optional::begin (C++26)

optional::end (C++26)

Monadic operations

optional::and_then (C++23)

optional::transform (C++23)

optional::or_else (C++23)

Modifiers

optional::emplace

optional::swap

optional::reset

Non-member functions

operator==operator!=operator<operator<=operator>operator>=operator<=> (C++20)

make_optional

swap(std::optional)

Deduction guides

Helper classes

hash<std::optional>

nullopt_t

in_place_t

bad_optional_access

Helper objects

nullopt

in_place

 

constexpr const T* operator->() const noexcept;	(1)	(since C++17)
constexpr T* operator->() noexcept;	(2)	(since C++17)
constexpr const T& operator*() const& noexcept;	(3)	(since C++17)
constexpr T& operator*() & noexcept;	(4)	(since C++17)
constexpr const T&& operator*() const&& noexcept;	(5)	(since C++17)
constexpr T&& operator*() && noexcept;	(6)	(since C++17)

Accesses the contained value.

1,2) Returns a pointer to the contained value.

3-6) Returns a reference to the contained value.

If has_value() is false, the behavior is undefined.	(until C++26)
If has_value() is false: If the implementation is hardened, a contract violation occurs. Moreover, if the contract-violation handler returns under “observe” evaluation semantic, the behavior is undefined. If the implementation is not hardened, the behavior is undefined.	(since C++26)

Return value

1,2) val

3,4) *val

5,6) std::move(*val )

Notes

This operator does not check whether *this contains a value, users can do so manually by using has_value() or operator bool(). Alternatively, if checked access is needed, value() or value_or() may be used.

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

value	returns the contained value (public member function)
value_or	returns the contained value if available, another value otherwise (public member function)