absl::optional_ref

A std::optional‐like interface around a T*.

Synopsis

Declared in <absl/types/optional_ref.h>

template<typename T>
class optional_ref;

Description

Similar to C++26's std::optional<T&>, but it also permits construction from rvalues. It makes it easier for functions to accept nullable object addresses, regardless of whether they point to temporaries. It is trivially copyable and destructible, so it should be passed by value.

Type Aliases

Name

Description

The referenced value type.

Member Functions

Name

Description

optional_ref [constructor]

Constructors

operator= [deleted]

Assignment is deleted; optional_ref is not assignable.

Represents the optional_ref as a std::optional.

Represents the optional_ref as a T* pointer.

Determines whether the optional_ref contains a value.

Accesses the underlying value; undefined behavior if empty.

Accesses members of the underlying value; undefined behavior if empty.

Returns a reference to the underlying value.

Returns the value if present, otherwise default_value.

Deduction Guides

Name

Description

optional_ref<T>

Deduces optional_ref<T> from a mutable lvalue.

optional_ref<T>

Deduces optional_ref<T> from a mutable std::optional.

optional_ref<T>

Deduces optional_ref<T> from a pointer.

optional_ref<T const>

Deduces optional_ref<const T> from a const lvalue.

optional_ref<T const>

Deduces optional_ref<const T> from a const std::optional.

Non-Member Functions

Name

Description

Tests whether two `optional_ref`s differ.

Tests whether an optional_ref differs from a value.

Tests whether an optional_ref holds a value.

Compares the referenced value of an optional_ref to a value.

Tests whether an optional_ref is empty.

Compares the referenced values of two `optional_ref`s.

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