std::optional<T>::and_then

< cpp‎ | utility‎ | optional
template< class F >
constexpr auto and_then( F&& f ) &;
 (1) (since C++23)
template< class F >
constexpr auto and_then( F&& f ) const&;
 (2) (since C++23)
template< class F >
constexpr auto and_then( F&& f ) &&;
 (3) (since C++23)
template< class F >
constexpr auto and_then( F&& f ) const&&;
 (4) (since C++23)

Returns the result of invocation of f on the contained value if it exists. Otherwise, returns an empty value of the return type.

The return type (see below) must be a specialization of std::optional. Otherwise, the program is ill-formed.

1) Equivalent to
if (*this)

    return std::invoke(std::forward<F>(f), this->value());
else

    return std::remove_cvref_t<std::invoke_result_t<F, T&>>();.
2) Equivalent to
if (*this)

    return std::invoke(std::forward<F>(f), this->value());
else

    return std::remove_cvref_t<std::invoke_result_t<F, const T&>>();.
3) Equivalent to
if (*this)

    return std::invoke(std::forward<F>(f), std::move(this->value()));
else

    return std::remove_cvref_t<std::invoke_result_t<F, T>>();.
4) Equivalent to
if (*this)

    return std::invoke(std::forward<F>(f), std::move(this->value()));
else

    return std::remove_cvref_t<std::invoke_result_t<F, const T>>();.

Parameters

f - a suitable function or Callable object that returns an std::optional

Return value

The result of f or an empty std::optional, as described above.

Notes

Some languages call this operation flatmap.

Example

This section is incomplete
Reason: no example

See also

 returns the contained value if available, another value otherwise
(public member function)
(C++23)
 returns an optional containing the transformed contained value if it exists, or an empty optional otherwise
(public member function)
(C++23)
 returns the optional itself if it contains a value, or the result of the given function otherwise
(public member function)