unique_ptr Class

Article
01/12/2013

Stores a pointer to an owned object. The object is owned by no other unique_ptr. The object is destroyed when the unique_ptr is destroyed.

template<class Type, class Del = default_delete<Type> >
    class unique_ptr {

public:
        typedef Type element_type;
        typedef Del deleter_type;
        typedef T1 pointer;

        unique_ptr ();
        unique_ptr (
            nullptr_t _Nptr
        );
        explicit unique_ptr (
            pointer _Ptr
        );
        unique_ptr (
            pointer _Ptr,
            typename conditional<
                is_reference<Del>::value, 
                Del,
                typename add_reference<const Del>::type
            >::type _Deleter
        );
        unique_ptr (
            pointer _Ptr,
            typename remove_reference<Del>::type&& _Deleter
        );
        unique_ptr (
            unique_ptr&& _Right
        );
        template<class Type2, Class Del2>
            unique_ptr (
                unique_ptr<Type2, Del2>&& _Right
            );

    ~unique_ptr ();

    unique_ptr& operator= (
        unique_ptr&& _Right
    );
    template<class Type2, Class Del2>
        unique_ptr& operator= (
            unique_ptr<Type2, Del2>&& _Right
        );
    void swap (
        unique_ptr& _Right
    );
    pointer release ();
    void reset (
       pointer _Ptr = pointer()
    );

    pointer get () const;
    Type& operator* () const;
    pointer operator-> () const;
    Del& get_deleter ();
    const Del& get_deleter () const;
    explicit operator bool () const;

    unique_ptr(
        const unique_ptr& _Right
) = delete;
    unique_ptr& operator=(
        const unique_ptr& _Right
) = delete;

private:
    pointer stored_ptr;    // exposition only
    Del stored_deleter;    // exposition only
    };

Parameters

_Right
A unique_ptr.
_Nptr
An rvalue of type std::nullptr_t.
_Ptr
A pointer.
_Deleter
A deleter function that is bound to a unique_ptr.

Exceptions

No exceptions are generated by unique_ptr.

Remarks

The unique_ptr class supersedes auto_ptr, and can be used as an element of STL containers.

unique_ptr uniquely manages a resource. Each unique_ptr object stores a pointer to the object that it owns or stores a null pointer. A resource can be owned by no more than one unique_ptr object; when a unique_ptr object that owns a particular resource is destroyed, the resource is freed. A unique_ptr object may be moved, but not copied; for more information, see Rvalue Reference Declarator: &&.

The resource is freed by calling a stored deleter object of type Del that knows how resources are allocated for a particular unique_ptr. The default deleterdefault_delete<Type> assumes that the resource pointed to by _Ptr is allocated with new, and that it can be freed by calling delete _Ptr. (A partial specialization **unique_ptr<Type[]>**manages array objects allocated with new[], and has the default deleterdefault_delete<Type[]>, specialized to call delete[] _Ptr.)

The stored pointer to an owned resource, stored_ptr has type pointer. It is Del::pointer if defined, and Type * if not. The stored deleter object stored_deleter occupies no space in the object if the deleter is stateless. Note that Del can be a reference type.

Members

Constructors

unique_ptr::unique_ptr

There are seven constructors for unique_ptr.

Typedefs

deleter_type	A synonym for the template parameter Del.
element_type	A synonym for the template parameter Type.
pointer	A synonym for Del::pointer if defined, otherwise Type *.

Member Functions

unique_ptr::get	Returns stored_ptr.
unique_ptr::get_deleter	Returns a reference to stored_deleter.
unique_ptr::release	stores pointer() in stored_ptr and returns its previous contents.
unique_ptr::reset	Releases the currently owned resource and accepts a new resource.
unique_ptr::swap	Exchanges resource and deleter with the provided unique_ptr.

Operators

operator bool	The operator returns a value of a type that is convertible to bool. The result of the conversion to bool is true when get() != pointer(), otherwise false.
operator->	The member function returns stored_ptr.
operator*	The member function returns*stored_ptr.
unique_ptr operator=	Assigns the value of a unique_ptr (or a pointer-type) to the current unique_ptr.

Requirements

Header: <memory>

Namespace: std

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