std::unique_ptr::reset

members of the primary template, unique_ptr<T>
void reset( pointer ptr = pointer() );	(1)
members of the specialization unique_ptr<T[]>
void reset( pointer ptr = pointer() );	(2)	(until C++17)
	(3)
template< class U > void reset( U ) = delete;	(until C++17)
template< class U > void reset( U );	(since C++17)
	(4)
void reset( std::nullptr_t p );	(until C++17)
void reset( std::nullptr_t p = nullptr );	(since C++17)

替换托管对象。

1%29current_ptr管理的指针。*this执行下列操作：

保存当前指针的副本。old_ptr = current_ptr

用参数覆盖当前指针。current_ptr = ptr

如果旧指针不是空的，则删除以前托管的对象。if(old_ptr != nullptr) get_deleter()(old_ptr)...

2) Behaves the same as the reset member of the primary template. 3) In the specialization for dynamic arrays, std::unique_ptr<T[]>, this template member is provided to prevent using reset() with a pointer to derived (which would result in undefined behavior with arrays). 4) In the specialization for dynamic arrays, std::unique_ptr<T[]>, this overload is necessary to allow reset to nullptr (which would otherwise be prohibited by the template overload). Equivalent to reset(pointer())	(until C++17)
3) 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 as pointer, or pointer is the same type as element_type* and U is a pointer type V* such that V()[] is convertible to element_type()[]. 4) Equivalent to reset(pointer())	(since C++17)

2) Behaves the same as the reset member of the primary template. 3) In the specialization for dynamic arrays, std::unique_ptr<T[]>, this template member is provided to prevent using reset() with a pointer to derived (which would result in undefined behavior with arrays). 4) In the specialization for dynamic arrays, std::unique_ptr<T[]>, this overload is necessary to allow reset to nullptr (which would otherwise be prohibited by the template overload). Equivalent to reset(pointer())

(until C++17)

3) 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 as pointer, or pointer is the same type as element_type* and U is a pointer type V* such that V(*)[] is convertible to element_type(*)[]. 4) Equivalent to reset(pointer())

(since C++17)

U是与pointer，或

pointer是与element_type*和U是指针类型。V*使...V(*)[]可转换为element_type(*)[]...

4%29相当于reset(pointer())%28自C++17%29

参数

ptr	-	pointer to a new object to manage

返回值

%280%29

例外

noexcept规格：

noexcept

注记

若要在提供新删除项的同时替换托管对象，可以使用移动赋值操作符。

自我重置的测试，即是否ptr指向已由*this不执行，除非作为编译器扩展或调试断言提供。注意，代码如p.reset(p.release())不涉及自重置，只涉及类似的代码p.reset(p.get())是的。

例

二次

#include <iostream>
#include <memory>
 
struct Foo {
    Foo() { std::cout << "Foo...\n"; }
    ~Foo() { std::cout << "~Foo...\n"; }
};
 
struct D {
    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);      
}

二次

产出：

二次

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...

二次

另见

release	returns a pointer to the managed object and releases the ownership (public member function)

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最后更新于：2017-12-18