class template

std::reference_wrapper

template <class T> class reference_wrapper;

Reference wrapper

Class that emulates a reference to an element of type T, but which can be copied (it is both copy-constructible and copy-assignable).

Template parameters

T: Type of the referred element.
This can either be an object or a function.

Member types

member type	definition
`type`	The template parameter (`T`)
`result_type`	If `T` is a pointer to function or to member function type: the return type of `T`. If `T` is a class, and has a `result_type` member: `T::result_type`. Otherwise, not defined.
`argument_type`	If `T` is a function type or a pointer to function type taking a single argument: the type of the argument taken by `T`. If `T` is a pointer to member function: the class type of which `T` is a member (with the same const/volatile qualification as the member function). If `T` is a class, and has an `argument_type` member: `T::argument_type`. Otherwise, not defined.
`first_argument_type`	If `T` is a function type or a pointer to function type taking two arguments: the type of the first argument taken by `T`. If `T` is a pointer to member function taking a single argument: the class type of which `T` is a member (with the same const/volatile qualification as the member function). If `T` is a class, and has an `first_argument_type` member: `T::first_argument_type`. Otherwise, not defined.
`second_argument_type`	If `T` is a function type or a pointer to function type taking two arguments: The type of the second argument taken by `T`. If `T` is a pointer to member function taking a single argument: the argument taken by `T`. If `T` is a class, and has an `second_argument_type` member: `T::second_argument_type`. Otherwise, not defined.

Note that, except for type, the other member types are not always defined.

Member functions

(constructor): Construct reference wrapper (public member function )

operator=: Copy assignment (public member function )

get: Access element (public member function )

operator(): Access element (functional form) (public member function )

operator type: Cast to reference (public member function )

Non-member helper functions

ref: Construct reference_wrapper (function template )

cref: Construct reference_wrapper to const (function template )

Example

// reference_wrapper example:
#include <iostream>     // std::cout
#include <functional>   // std::reference_wrapper

int main () {
  int a(10),b(20),c(30);

  // an array of "references":
  std::reference_wrapper<int> refs[] = {a,b,c};

  std::cout << "refs:";
  for (int& x : refs) std::cout << ' ' << x;
  std::cout << '\n';

  return 0;
}