std::ref
Defined in header <functional> | | |
|---|---|---|
template< class T > std::reference_wrapper<T> ref(T& t); | (1) | (since C++11) |
template< class T > std::reference_wrapper<T> ref( std::reference_wrapper<T> t ); | (2) | (since C++11) |
template <class T> void ref(const T&&) = delete; | (3) | (since C++11) |
template< class T > std::reference_wrapper<const T> cref( const T& t ); | (4) | (since C++11) |
template< class T > std::reference_wrapper<const T> cref( std::reference_wrapper<T> t ); | (5) | (since C++11) |
template <class T> void cref(const T&&) = delete; | (6) | (since C++11) |
函数模板ref和cref是生成类型对象的助手函数。std::reference_wrapper，使用模板参数推导若要确定结果的模板参数，请执行以下操作。
参数
t | - | lvalue reference to object that needs to be wrapped or an instance of std::reference_wrapper |
|---|
返回值
1%29std::reference_wrapper<T>(t)
2%29ref(t.get())
4%29std::reference_wrapper<const T>(t)
5%29cref(t.get())
3，6%29 rvalue参考包装被删除。
例外
noexcept规格：
noexcept
例
二次
#include <functional>
#include <iostream>
void f(int& n1, int& n2, const int& n3)
{
std::cout << "In function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
++n1; // increments the copy of n1 stored in the function object
++n2; // increments the main()'s n2
// ++n3; // compile error
}
int main()
{
int n1 = 1, n2 = 2, n3 = 3;
std::function<void()> bound_f = std::bind(f, n1, std::ref(n2), std::cref(n3));
n1 = 10;
n2 = 11;
n3 = 12;
std::cout << "Before function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
bound_f();
std::cout << "After function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
}二次
产出：
二次
Before function: 10 11 12
In function: 1 11 12
After function: 10 12 12二次
另见
reference_wrapper (C++11) | CopyConstructible and CopyAssignable reference wrapper (class template) |
|---|
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