std::hash<std::unique_ptr>

 

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std::unique_ptr

成员函数

unique_ptr::unique_ptr

unique_ptr::~unique_ptr

unique_ptr::operator=

修饰符

unique_ptr::release

unique_ptr::reset

unique_ptr::swap

观察者

unique_ptr::get

unique_ptr::get_deleter

unique_ptr::operator bool

unique_ptr::operator*unique_ptr::operator->

unique_ptr::operator[]

非成员函数

make_uniquemake_unique_for_overwrite (C++14)(C++20)

operator==operator!=operator<operator>operator<=operator>=operator<=> (直到 C++20)(C++20)

operator<< (C++20)

swap(std::unique_ptr)

辅助类

hash<std::unique_ptr>

 

template< class T, class Deleter > struct hash<std::unique_ptr<T, Deleter>>;		(自 C++11 起)

对于 std::unique_ptr<T, Deleter>，std::hash 的模板特化允许用户获取类型为 std::unique_ptr<T, Deleter> 的对象的哈希值。

如果 std::hash<typename std::unique_ptr<T,D>::pointer> 已启用，则启用特化 std::hash<std::unique_ptr<T,D>> （参见 std::hash），否则禁用。

启用后，对于给定的 std::unique_ptr<T, D> p，此特化确保 std::hash<std::unique_ptr<T, D>>()(p) == std::hash<typename std::unique_ptr<T, D>::pointer>()(p.get()).

此特化的成员函数不保证是 noexcept，因为指针可能是一个花哨的指针，它的哈希值可能抛出异常。

示例

运行此代码

#include <functional>
#include <iostream>
#include <memory>
 
struct Foo
{
    Foo(int num) : nr(num) { std::cout << "Foo(" << nr << ")\n"; }
 
    ~Foo() { std::cout << "~Foo()\n"; }
 
    bool operator==(const Foo &other) const { return nr == other.nr; };
 
    int nr;
};
 
int main()
{
    std::cout << std::boolalpha << std::hex;
 
    Foo* foo = new Foo(5);
    std::unique_ptr<Foo> up(foo); 
    std::cout << "hash(up):    " << std::hash<std::unique_ptr<Foo>>()(up) << '\n'
              << "hash(foo):   " << std::hash<Foo*>()(foo) << '\n'
              << "*up==*foo:   " << (*up == *foo) << "\n\n";
 
    std::unique_ptr<Foo> other = std::make_unique<Foo>(5);
    std::cout << "hash(up):    " << std::hash<std::unique_ptr<Foo>>()(up) << '\n'
              << "hash(other): " << std::hash<std::unique_ptr<Foo>>()(other) << '\n'
              << "*up==*other: " <<(*up == *other) << "\n\n";
}

可能的输出

Foo(5)
hash(up):    acac20
hash(foo):   acac20
*up==*foo:   true
 
Foo(5)
hash(up):    acac20
hash(other): acbc50
*up==*other: true
 
~Foo()
~Foo()

另请参阅

hash (C++11)

哈希函数对象 (类模板)