std::shared_ptr<T>::unique

 

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std::shared_ptr

Member functions

shared_ptr::shared_ptr

shared_ptr::~shared_ptr

shared_ptr::operator=

Modifiers

shared_ptr::reset

shared_ptr::swap

Observers

shared_ptr::get

shared_ptr::operator*shared_ptr::operator->

shared_ptr::operator[] (C++17)

shared_ptr::use_count

shared_ptr::unique (until C++20*)

shared_ptr::operator bool

shared_ptr::owner_before

shared_ptr::owner_hash (C++26)

shared_ptr::owner_equal (C++26)

Non-member functions

swap(std::shared_ptr)

make_sharedmake_shared_for_overwrite (C++20)

allocate_sharedallocate_shared_for_overwrite (C++20)

static_pointer_castdynamic_pointer_castconst_pointer_castreinterpret_pointer_cast (C++17)

get_deleter

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

operator<<

atomic_xxx functions (until C++26*)

Helper classes

atomic<std::shared_ptr> (C++20)

hash<std::shared_ptr>

Deduction guides(C++17)

 

bool unique()constnoexcept;		(deprecated in C++17) (removed in C++20)

Checks if *this is the only shared_ptr instance managing the current object, i.e. whether use_count()==1.

Parameters

(none)

Return value

true if *this is the only shared_ptr instance managing the current object, false otherwise.

Notes

This function was deprecated in C++17 and removed in C++20 because use_count()==1 is meaningless in multithreaded environment (see Notes in use_count).

Example

Run this code

#include <iostream> #include <memory>    int main(){auto sp1 =std::make_shared<int>(5);std::cout<<std::boolalpha;std::cout<<"sp1.unique() == "<< sp1.unique()<<'\n';   std::shared_ptr<int> sp2 = sp1;std::cout<<"sp1.unique() == "<< sp1.unique()<<'\n';}

Output:

sp1.unique() == true sp1.unique() == false

See also

use_count

returns the number of shared_ptr objects referring to the same managed object (public member function)