class FunctionRef

FunctionRef

An `absl::FunctionRef` is a lightweight wrapper to any invocable object with

a compatible signature. Generally, an `absl::FunctionRef` should only be used

as an argument type and should be preferred as an argument over a const

reference to a `std::function`. `absl::FunctionRef` itself does not allocate,

although the wrapped invocable may.

Example:

// The following function takes a function callback by const reference

bool Visitor(const std::function

<void

(my_proto

&

,

absl::string_view)>

&

callback);

// Assuming that the function is not stored or otherwise copied, it can be

// replaced by an `absl::FunctionRef`:

bool Visitor(absl::FunctionRef

<void

(my_proto

&

, absl::string_view)>

callback);

Note: the assignment operator within an `absl::FunctionRef` is intentionally

deleted to prevent misuse; because the `absl::FunctionRef` does not own the

underlying type, assignment likely indicates misuse.