NAME¶

std::expected::operator->,std::expected::operator* - std::expected::operator->,std::expected::operator*

Synopsis¶

T is not cv void
constexpr const T* operator->() const noexcept; (1) (since C++23)
constexpr T* operator->() noexcept; (1) (since C++23)
constexpr const T& operator*() const& noexcept; (2) (since C++23)
constexpr T& operator*() & noexcept; (2) (since C++23)
constexpr const T&& operator*() const&& noexcept; (2) (since C++23)
constexpr T&& operator*() && noexcept; (2) (since C++23)
T is cv void
constexpr void operator*() const noexcept; (3) (since C++23)

Accesses the expected value contained in *this.

1) Returns a pointer to the contained value.
2) Returns a reference to the contained value.
3) Returns nothing.

The behavior is undefined if this->has_value() is false.

Parameters¶

(none)

Return value¶

Pointer or reference to the contained value.

Notes¶

These operators do 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 <cassert>
#include <expected>
#include <iomanip>
#include <iostream>
#include <string>

int main()
{
using namespace std::string_literals;

std::expected<int, std::string> ex1 = 6;
assert(*ex1 == 6);

*ex1 = 9;
assert(*ex1 == 9);

ex1 = std::unexpected("error"s);
// *ex1 = 13 // UB, ex1 contains "unexpected" value
assert(ex1.value_or(42) == 42);

std::expected<std::string, bool> ex2 = "Moon"s;
std::cout << "ex2: " << std::quoted(*ex2) << ", size: " << ex2->size() << '\n';

// You can "take" the contained value by calling operator* on an rvalue to expected

auto taken = *std::move(ex2);
std::cout << "taken: " << std::quoted(taken) << "\n"
"ex2: " << std::quoted(*ex2) << ", size: " << ex2->size() << '\n';
}

Possible output:¶

ex2: "Moon", size: 4
taken: "Moon"
ex2: "", size: 0

See also¶

value returns the expected value
(public member function)
value_or returns the expected value if present, another value otherwise
(public member function)
operator bool checks whether the object contains an expected value
has_value (public member function)
error returns the unexpected value
(public member function)