std::unique_ptr<T,Deleter>::reset
From cppreference.com
< cpp | memory | unique ptr
members of the primary template, unique_ptr<T> |
||
void reset( pointer ptr = pointer() ) noexcept; |
(1) | (constexpr since C++23) |
members of the specialization unique_ptr<T[]> |
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template< class U > void reset( U ptr ) noexcept; |
(2) | (constexpr since C++23) |
void reset( std::nullptr_t = nullptr ) noexcept; |
(3) | (constexpr since C++23) |
Replaces the managed object.
1) Given
current_ptr
, the pointer that was managed by *this, performs the following actions, in this order:
- Saves a copy of the current pointer old_ptr = current_ptr.
- Overwrites the current pointer with the argument current_ptr = ptr.
- If the old pointer was non-empty, deletes the previously managed object if (old_ptr) get_deleter()(old_ptr).
2) Behaves the same as the reset member of the primary template, except that it will only participate in overload resolution if either
-
U
is the same type aspointer
, or -
pointer
is the same type aselement_type*
andU
is a pointer typeV*
such thatV(*)[]
is convertible toelement_type(*)[]
.
3) Equivalent to reset(pointer()).
Contents |
[edit] Parameters
ptr | - | pointer to a new object to manage |
[edit] Return value
(none)
[edit] Notes
To replace the managed object while supplying a new deleter as well, move assignment operator may be used.
A test for self-reset, i.e. whether ptr points to an object already managed by *this, is not performed, except where provided as a compiler extension or as a debugging assert. Note that code such as p.reset(p.release()) does not involve self-reset, only code like p.reset(p.get()) does.
[edit] Example
Run this code
#include <iostream> #include <memory> struct Foo // object to manage { Foo() { std::cout << "Foo...\n"; } ~Foo() { std::cout << "~Foo...\n"; } }; struct D // deleter { void operator() (Foo* p) { std::cout << "Calling delete for Foo object... \n"; delete p; } }; int main() { std::cout << "Creating new Foo...\n"; std::unique_ptr<Foo, D> up(new Foo(), D()); // up owns the Foo pointer (deleter D) std::cout << "Replace owned Foo with a new Foo...\n"; up.reset(new Foo()); // calls deleter for the old one std::cout << "Release and delete the owned Foo...\n"; up.reset(nullptr); }
Output:
Creating new Foo... Foo... Replace owned Foo with a new Foo... Foo... Calling delete for Foo object... ~Foo... Release and delete the owned Foo... Calling delete for Foo object... ~Foo...
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 2118 | C++11 | unique_ptr<T[]>::reset rejected qualification conversions
|
accepts |
[edit] See also
returns a pointer to the managed object and releases the ownership (public member function) |