C++

参考

<functional>

reference_wrapper

public member function
<functional>

std::reference_wrapper::reference_wrapper

初始化 (1)
reference_wrapper (type& ref) noexcept;reference_wrapper (type&&) = delete;
复制 (2)
reference_wrapper (const reference_wrapper& x) noexcept;
Construct reference wrapper
Constructs a reference_wrapper object

(1) initialization
The object stores a reference to ref.
Note that this constructor only accepts lvalues (the rvalue version is deleted).
(2) copy
The object stores a reference to the same object or function x does (x.get()).

参数

ref
An lvalue reference, whose reference is stored in the object.
type 是一个描述被引用类型的成员类型（它是类模板参数 T 的别名）。
x
A reference_wrapper object of the same type (i.e., with the same template parameter, T).

示例

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// 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;
}

输出
refs: 10 20 30


数据竞争

The initialization constructor (1) does not access ref, but it acquires a reference to it, which can be used to access or modify it.
The copy constructor (2) accesses its argument (x), acquiring a reference to its referred element, which can be used to access or modify it.

异常安全

无异常保证： 绝不抛出异常。

另见

ref
构造 reference_wrapper (函数模板)
cref
构造指向 const 的 reference_wrapper (函数模板)
reference_wrapper::operator=
Copy assignment (public member function)
reference_wrapper::get
访问元素 (公开成员函数)