std::owner_less

STD：业主[医]再少点

Defined in header
	(1)
template< class T > struct owner_less; /* undefined */	(since C++11) (until C++17)
template< class T = void > struct owner_less; /* undefined */	(since C++17)
template< class T > struct owner_less<std::shared_ptr<T>>;	(2)	(since C++11)
template< class T > struct owner_less<std::weak_ptr<T>>;	(3)	(since C++11)
template<> struct owner_less<void>;	(4)	(since C++17)

此函数对象提供基于所有者的%28 AS，而不是两者的基于值的%29混合类型排序。std::weak_ptr和std::shared_ptr.顺序是这样的，只有当两个智能指针都是空的，或者它们都管理同一个对象时，它们才能比较等价的值，即使get()是不同的。因为它们指向同一对象%29内的不同子对象。

类模板是构建关联容器时的首选比较谓词。std::shared_ptr或std::weak_ptr作为钥匙，也就是说，

std::map<std::shared_ptr<T>, U,std::owner_less<std::shared_ptr<T>>>

或者。

std::map<std::weak_ptr<T>, U,std::owner_less<std::weak_ptr<T>>>...

默认operator<不是为弱指针定义的，并且可能错误地考虑了同一个对象的两个共享指针---非等效的%28(请参见shared_ptr::owner_before29%。

专门性

The standard library provides a specialization of std::owner_less when T is not specified. In this case, the parameter types are deduced from the arguments (each of which must still be either a std::shared_ptr or a std::weak_ptr). owner_less function object providing mixed-type owner-based ordering of shared and weak pointers, regardless of the type of the pointee (class template specialization)	owner_less	function object providing mixed-type owner-based ordering of shared and weak pointers, regardless of the type of the pointee (class template specialization)	(since C++17)
owner_less<void>	function object providing mixed-type owner-based ordering of shared and weak pointers, regardless of the type of the pointee (class template specialization)

成员类型

Member type	Definition
result_type(deprecated in c++17)	2-3) bool
first_argument_type(deprecated in c++17)	2) std::shared_ptr<T>3) std::weak_ptr<T>
second_argument_type(deprecated in c++17)	2) std::shared_ptr<T>3) std::weak_ptr<T>

成员函数

operator()	compares its arguments using owner-based semantics (function)

STD：业主[医]减：：操作员%28%29

bool operator()( const std::shared_ptr& lhs, const std::shared_ptr& rhs ) const;		(since C++11) (member only of owner_less> template specialization)
bool operator()( const std::shared_ptr<T>& lhs, const std::weak_ptr<T>& rhs ) const;		(since C++11)
bool operator()( const std::weak_ptr<T>& lhs, const std::shared_ptr<T>& rhs ) const;		(since C++11)
bool operator()( const std::weak_ptr<T>& lhs, const std::weak_ptr<T>& rhs ) const;		(since C++11) (member only of owner_less<weak_ptr<T>> template specialization)

比较lhs和rhs使用基于所有者的语义。有效呼叫lhs.owner_before(rhs)...

排序是严格弱序关系。

lhs和rhs只有当它们都是空的或共享的所有权时，它们才是等价的。

参数

lhs, rhs	-	shared-ownership pointers to compare

返回值

true如果lhs是少于rhs由业主依据订单确定。

例外

(none)	(until C++17)
noexcept specification: noexcept	(since C++17)

另见

owner_before	provides owner-based ordering of shared pointers (public member function of std::shared_ptr)
owner_before	provides owner-based ordering of weak pointers (public member function of std::weak_ptr)

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