std::reference_wrapper

 

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initializer_list （C++11）

bitset

hash （C++11）

关系运算符 Original: Relational operators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

rel_ops::operator!= rel_ops::operator> rel_ops::operator<= rel_ops::operator>=

双和元组 Original: Pairs and tuples The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

pair

tuple （C++11）

piecewise_construct_t （C++11）

piecewise_construct （C++11）

掉期，远期和移动 Original: Swap, forward and move The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

swap

forward （C++11）

move （C++11）

move_if_noexcept （C++11）

declval （C++11）

 

函数对象

功能包装 Original: Function wrappers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
function （C++11）
mem_fn （C++11）
bad_function_call （C++11）
绑定 Original: Bind The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
bind （C++11）
is_bind_expression （C++11）
is_placeholder （C++11）
_1, _2, _3, ... （C++11）
参考包装 Original: Reference wrappers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
reference_wrapper （C++11）
ref cref （C++11） （C++11）
操作包装 Original: Operator wrappers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
plus minus negate multiplies divides modulus logical_and logical_or logical_not	equal_to not_equal_to greater less greater_equal less_equal bit_and bit_or bit_xor
否定词 Original: Negators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
unary_negate binary_negate	not1 not2
已过时粘合剂和适配器 Original: Deprecated binders and adaptors The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
unary_function （过时了）
binary_function （过时了）
ptr_fun （过时了）
pointer_to_unary_function （过时了）
pointer_to_binary_function （过时了）
mem_fun （过时了）
mem_fun_t mem_fun1_t const_mem_fun_t const_mem_fun1_t （过时了） （过时了） （过时了） （过时了）
mem_fun_ref （过时了）
mem_fun_ref_t mem_fun1_ref_t const_mem_fun_ref_t const_mem_fun1_ref_t （过时了） （过时了） （过时了） （过时了）
binder1st binder2nd （过时了） （过时了）
bind1st bind2nd （过时了） （过时了）

 

std::reference_wrapper

成员函数 Original: Member functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

reference_wrapper::reference_wrapper

reference_wrapper::operator=

reference_wrapper::get reference_wrapper::operator T&

reference_wrapper::operator()

 

Defined in header <functional>
template< class T > class reference_wrapper;		（C++11 起）

类模板std::reference_wrapper是一个CopyConstructible和CopyAssignable的包装对象或引用的类型T的参考。 std::reference_wrapper实例对象（可以被复制或存储在容器中），但它们是隐式转换T&，使它们可以被用来作为参数的功能，采取通过引用基础类型.

Original:

Class template std::reference_wrapper is a CopyConstructible and CopyAssignable wrapper around a reference to object or reference to function of type T. Instances of std::reference_wrapper are objects (can be copied or stored in containers), but they are implicitly convertible to T&, so that they can be used as arguments with the functions that take the underlying type by reference.

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Helper函数std::ref和std::cref也常常用于生成std::reference_wrapper对象.

Original:

Helper functions std::ref and std::cref are often used to generate std::reference_wrapper objects.

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std::reference_wrapper也可用于std::bind或参考std::thread的构造函数来传递对象.

Original:

std::reference_wrapper is also used to pass objects to std::bind or to the constructor of std::thread by reference.

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会员类型

类型 Original: type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.	definition
type	T
result_type	T如果T的返回类型是一个函数。否则，没有定义 Original: The return type of T if T is a function. Otherwise, not defined The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
argument_type	1）如果T是一个函数或函数指针，它有一个参数的类型A1，然后argument_type是A1. 2）如果T是一个T0不带任何参数类的成员函数的指针，然后argument_type是T0*，可能CV-qualified 3）如果T是一个类类型的成员类型T::argument_type，然后argument_type是一个别名 Original: 1) if T is a function or pointer to function that takes one argument of type A1, then argument_type is A1. 2) if T is a pointer to member function of class T0 that takes no arguments, then argument_type is T0*, possibly cv-qualified 3) if T is a class type with a member type T::argument_type, then argument_type is an alias of that The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
first_argument_type	1）如果T是一个函数或指针的函数，它接受两个参数类型为SA1和A2，然后first_argument_type是A1. 2）如果T是一个指针，指向成员函数的类T0它有一个参数，然后first_argument_type是T0*，可能CV-qualified 3）如果T是一个类类型的成员类型T::first_argument_type，然后first_argument_type是一个别名 Original: 1) if T is a function or pointer to function that takes two arguments of type s A1 and A2, then first_argument_type is A1. 2) if T is a pointer to member function of class T0 that takes one argument, then first_argument_type is T0*, possibly cv-qualified 3) if T is a class type with a member type T::first_argument_type, then first_argument_type is an alias of that The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
second_argument_type	1）如果T是一个函数或指针的函数，它接受两个参数类型为SA1和A2，然后second_argument_type是A2. 2）如果T是一个T0它有一个参数A1类的成员函数的指针，然后second_argument_type是A1，可能CV-qualified 3）如果T是一个类类型的成员类型T::second_argument_type，然后first_argument_type是一个别名 Original: 1) if T is a function or pointer to function that takes two arguments of type s A1 and A2, then second_argument_type is A2. 2) if T is a pointer to member function of class T0 that takes one argument A1, then second_argument_type is A1, possibly cv-qualified 3) if T is a class type with a member type T::second_argument_type, then first_argument_type is an alias of that The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

成员函数

(constructor)	存储一个参考在一个新std::reference_wrapper对象 Original: stores a reference in a new std::reference_wrapper object The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （公共成员函数）
operator=	重新绑定std::reference_wrapper Original: rebinds a std::reference_wrapper The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （公共成员函数）
get operator T&	访问所存储的参考 Original: accesses the stored reference The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （公共成员函数）
operator()	调用存储功能 Original: calls the stored function The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （公共成员函数）

为例

演示如何使用的reference_wrapper作为一个容器的引用，这使得它能够访问相同的容器中，使用多个索引

Original:

Demonstrates the use of reference_wrapper as a container of references, which makes it possible to access the same container using multiple indexes

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#include <algorithm>
#include <list>
#include <vector>
#include <iostream>
#include <functional>
 
int main()
{
    std::list<int> l = {-4, -3, -2, -1, 0, 1, 2, 3, 4};
 
    std::vector<std::reference_wrapper<int>> v(l.begin(), l.end());
    std::random_shuffle(v.begin(), v.end());
 
    std::vector<std::reference_wrapper<int>> v2(v.begin(), v.end());
    std::partition(v2.begin(), v2.end(), [](int n){return n<0;});
 
    std::cout << "Contents of the list: ";
    for(int n: l) {
        std::cout << n << ' ';
    }
    std::cout << '\n';
 
    std::cout << "Contents of the list, shuffled: ";
    for(int i: v) {
        std::cout << i << ' ';
    }
    std::cout << '\n';
 
    std::cout << "Shuffled elements, partitioned: ";
    for(int i: v2) {
        std::cout << i << ' ';
    }
    std::cout << '\n';
}

Output:

Contents of the list: -4 -3 -2 -1 0 1 2 3 4
Contents of the list, shuffled: 0 -1 3 4 -4 1 -2 -3 2
Shuffled elements, partitioned: -3 -1 -2 -4 4 1 3 0 2

另请参阅

ref cref （C++11） （C++11）	创建一个std::reference_wrapper推导出它的参数类型 Original: creates a std::reference_wrapper with a type deduced from its argument The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （函数模板）
bind （C++11）	绑定一个或多个参数的函数对象 Original: binds one or more arguments to a function object The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （函数模板）