std::swap(std::unique_ptr)

 

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Smart pointers unique_ptr (C++11) shared_ptr (C++11) weak_ptr (C++11) auto_ptr (until C++17*) owner_less (C++11) owner_less<void> (C++17) owner_hash (C++26) owner_equal (C++26) enable_shared_from_this (C++11) bad_weak_ptr (C++11) default_delete (C++11) out_ptr_t (C++23) inout_ptr_t (C++23) Low level memory management operator new operator new[] operator delete operator delete[] get_new_handler (C++11) set_new_handler launder (C++17) bad_alloc bad_array_new_length (C++11) nothrow_t align_val_t (C++17) destroying_delete_t (C++20) new_handler nothrow Miscellaneous pointer_traits (C++11) to_address (C++20) addressof (C++11) align (C++11) assume_aligned (C++20) C Library malloc calloc realloc    aligned_alloc (C++17) free

 

std::unique_ptr

Member functions

unique_ptr::unique_ptr

unique_ptr::~unique_ptr

unique_ptr::operator=

Modifiers

unique_ptr::release

unique_ptr::reset

unique_ptr::swap

Observers

unique_ptr::get

unique_ptr::get_deleter

unique_ptr::operator bool

unique_ptr::operator*unique_ptr::operator->

unique_ptr::operator[]

Non-member functions

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

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

operator<< (C++20)

swap(std::unique_ptr)

Helper classes

hash<std::unique_ptr>

 

Defined in header <memory>
template< class T, class D > void swap( std::unique_ptr<T, D>& lhs, std::unique_ptr<T, D>& rhs ) noexcept;		(since C++11) (constexpr since C++23)

Specializes the std::swap algorithm for std::unique_ptr. Swaps the contents of lhs and rhs. Calls lhs.swap(rhs).

This function does not participate in overload resolution unless std::is_swappable_v<D> is true.

(since C++17)

Parameters

lhs, rhs

-

smart pointers whose contents to swap

Return value

(none)

Complexity

Constant.

Example

Run this code

#include <iostream>
#include <memory>
#include <string>
 
struct Foo {
    Foo(int _val) : val(_val) { std::cout << "Foo...\n"; }
    ~Foo() { std::cout << "~Foo...\n"; }
    std::string print() { return std::to_string(val); }
    int val;
};
 
int main()
{
    std::unique_ptr<Foo> p1 = std::make_unique<Foo>(100);
    std::unique_ptr<Foo> p2 = std::make_unique<Foo>(200);
    auto print = [&]() {
        std::cout << " p1=" << (p1 ? p1->print() : "nullptr");
        std::cout << " p2=" << (p2 ? p2->print() : "nullptr") << '\n';  
    };
    print();
 
    std::swap(p1, p2);
    print();
 
    p1.reset();
    print();
 
    std::swap(p1, p2);
    print();   
}

Output:

Foo...
Foo...
 p1=100 p2=200
 p1=200 p2=100
~Foo...
 p1=nullptr p2=100
 p1=100 p2=nullptr
~Foo...

See also

swap	swaps the values of two objects (function template)
swap	swaps the contents (public member function)