std::optional::operator->, std::optional::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

Language
Standard Library Headers
Freestanding and hosted implementations
Named requirements
Language support library
Concepts library (C++20)
Diagnostics library
Utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications

Member functions
optional::optional
optional::~optional
optional::operator=
Observers
optional::operator->optional::operator*
optional::operator booloptional::has_value
optional::value
optional::value_or
Modifiers
optional::emplace
optional::swap
optional::reset
Non-member functions
operator==operator!=operator<operator<=operator>operator>=
make_optional
swap
Deduction guides
Helper classes
hash
nullopt_t
in_place_t
bad_optional_access
Helper objects
nullopt
in_place