utils::Required< T > Class Template Reference

#include <userver/utils/required.hpp>

Detailed Description

template<typename T>
class utils::Required< T >

A wrapper that holds a value of type T and has no default constructor, forcing explicit initialization.

Unlike std::optional, Required is always engaged after construction. It is useful for struct fields that must be explicitly set.

Example usage

struct MyConfig {
    utils::Required<std::string> name;
    utils::Required<int> timeout;
};

    MyConfig cfg{.name = "my-service", .timeout = 42};
    EXPECT_EQ(*cfg.name, "my-service");
    EXPECT_EQ(*cfg.timeout, 42);

Definition at line 29 of file required.hpp.

Public Member Functions
template<typename U = T> requires (!std::same_as<std::decay_t<U>, Required> && std::constructible_from<T, U &&>)
constexpr	explicit (!std::convertible_to< U &&, T >) Required(U &&value)
	Construct T from a value (conditionally explicit).
template<typename... Args> requires (sizeof...(Args) >= 2 && std::constructible_from<T, Args && ...>)
constexpr	Required (Args &&... args)
	Emplace-construct T from args.
	Required (const Required &)=default
Required &	operator= (const Required &)=default
	Required (Required &&)=default
Required &	operator= (Required &&)=default
constexpr T &	operator* () &noexcept USERVER_IMPL_LIFETIME_BOUND
	Access the contained value.
constexpr const T &	operator* () const &noexcept USERVER_IMPL_LIFETIME_BOUND
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
constexpr T &&	operator* () &&noexcept
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
constexpr T *	operator-> () noexcept USERVER_IMPL_LIFETIME_BOUND
	Access members of the contained value.
constexpr const T *	operator-> () const noexcept USERVER_IMPL_LIFETIME_BOUND
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
constexpr	operator T& () &noexcept USERVER_IMPL_LIFETIME_BOUND
	Implicit conversion to T&.
constexpr	operator const T & () const &noexcept USERVER_IMPL_LIFETIME_BOUND
	Implicit conversion to const T&.
template<typename U> requires (!std::same_as<U, T> && !std::is_reference_v<U> && std::convertible_to<const T&, U>)
constexpr	operator U () const
	Implicit conversion to any type that T is implicitly convertible to (by value).

Constructor & Destructor Documentation

Required()

template<typename T>

template<typename... Args>
requires (sizeof...(Args) >= 2 && std::constructible_from<T, Args && ...>)

utils::Required< T >::Required ( Args &&... args )

inlineexplicitconstexpr

Emplace-construct T from args.

Definition at line 43 of file required.hpp.

Member Function Documentation

explicit()

template<typename T>

template<typename U = T>
requires (!std::same_as<std::decay_t<U>, Required> && std::constructible_from<T, U &&>)

utils::Required< T >::explicit ( !std::convertible_to< U &&, T > ) &&

inlineconstexpr

Construct T from a value (conditionally explicit).

Definition at line 36 of file required.hpp.

operator const T &()

template<typename T>

utils::Required< T >::operator const T & ( ) const &

inlineconstexprnoexcept

Implicit conversion to const T&.

Definition at line 71 of file required.hpp.

operator T&()

template<typename T>

utils::Required< T >::operator T& ( ) &

inlineconstexprnoexcept

Implicit conversion to T&.

Definition at line 68 of file required.hpp.

operator U()

template<typename T>

template<typename U>
requires (!std::same_as<U, T> && !std::is_reference_v<U> && std::convertible_to<const T&, U>)

utils::Required< T >::operator U ( ) const

inlineconstexpr

Implicit conversion to any type that T is implicitly convertible to (by value).

Definition at line 76 of file required.hpp.

operator*() [1/3]

template<typename T>

T && utils::Required< T >::operator* ( ) &&

inlineconstexprnoexcept

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Definition at line 59 of file required.hpp.

operator*() [2/3]

template<typename T>

T & utils::Required< T >::operator* ( ) &

inlineconstexprnoexcept

Access the contained value.

Definition at line 53 of file required.hpp.

operator*() [3/3]

template<typename T>

const T & utils::Required< T >::operator* ( ) const &

inlineconstexprnoexcept

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Definition at line 56 of file required.hpp.

operator->() [1/2]

template<typename T>

const T * utils::Required< T >::operator-> ( ) const

inlineconstexprnoexcept

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Definition at line 65 of file required.hpp.

operator->() [2/2]

template<typename T>

T * utils::Required< T >::operator-> ( )

inlineconstexprnoexcept

Access members of the contained value.

Definition at line 62 of file required.hpp.

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The documentation for this class was generated from the following file:

• userver/utils/required.hpp