# Poco

# template < class C, class RC = ReferenceCounter, class RP = ReleasePolicy < C >>

# class SharedPtr

Library: Foundation
Package: Core
Header: Poco/SharedPtr.h

## Description

SharedPtr is a "smart" pointer for classes implementing reference counting based garbage collection. SharedPtr is thus similar to AutoPtr. Unlike the AutoPtr template, which can only be used with classes that support reference counting, SharedPtr can be used with any class. For this to work, a SharedPtr manages a reference count for the object it manages.

SharedPtr works in the following way: If an SharedPtr is assigned an ordinary pointer to an object (via the constructor or the assignment operator), it takes ownership of the object and the object's reference count is initialized to one. If the SharedPtr is assigned another SharedPtr, the object's reference count is incremented by one. The destructor of SharedPtr decrements the object's reference count by one and deletes the object if the reference count reaches zero. SharedPtr supports dereferencing with both the -> and the * operator. An attempt to dereference a null SharedPtr results in a NullPointerException being thrown. SharedPtr also implements all relational operators and a cast operator in case dynamic casting of the encapsulated data types is required.

## Member Summary

Member Functions: assign, cast, get, isNull, operator !, operator !=, operator *, operator <, operator <=, operator =, operator ==, operator >, operator >=, operator C *, operator const C *, operator->, referenceCount, reset, swap, unsafeCast

## Types Aliases

### Type

using Type = C;

## Constructors

### SharedPtr

SharedPtr();

### SharedPtr

SharedPtr(
C * ptr
);

### SharedPtr

template < class Other, class OtherRP > SharedPtr(
const SharedPtr < Other, RC, OtherRP > & ptr
);

### SharedPtr

SharedPtr(
const SharedPtr & ptr
);

### SharedPtr

SharedPtr(
SharedPtr && ptr
) noexcept;

## Destructor

### ~SharedPtr

~SharedPtr();

## Member Functions

### assign

SharedPtr & assign(
C * ptr
);

### assign

SharedPtr & assign(
const SharedPtr & ptr
);

### assign

template < class Other, class OtherRP > SharedPtr & assign(
const SharedPtr < Other, RC, OtherRP > & ptr
);

### cast

template < class Other > SharedPtr < Other, RC, RP > cast() const;

Casts the SharedPtr via a dynamic cast to the given type. Returns an SharedPtr containing nullptr if the cast fails. Example: (assume class Sub: public Super)

    SharedPtr<Super> super(new Sub());
    SharedPtr<Sub> sub = super.cast<Sub>();
    poco_assert (sub.get());

### get

C * get();

### get

const C * get() const;

### isNull

bool isNull() const;

### operator !

bool operator ! () const;

### operator !=

bool operator != (
const SharedPtr & ptr
) const;

### operator !=

bool operator != (
const C * ptr
) const;

### operator !=

bool operator != (
C * ptr
) const;

### operator !=

bool operator != (
std::nullptr_t ptr
) const;

### operator *

C & operator * ();

### operator *

const C & operator * () const;

### operator <

bool operator < (
const SharedPtr & ptr
) const;

### operator <

bool operator < (
const C * ptr
) const;

### operator <

bool operator < (
C * ptr
) const;

### operator <=

bool operator <= (
const SharedPtr & ptr
) const;

### operator <=

bool operator <= (
const C * ptr
) const;

### operator <=

bool operator <= (
C * ptr
) const;

### operator =

SharedPtr & operator = (
C * ptr
);

### operator =

SharedPtr & operator = (
const SharedPtr & ptr
);

### operator =

SharedPtr & operator = (
SharedPtr && ptr
) noexcept;

### operator =

template < class Other, class OtherRP > SharedPtr & operator = (
const SharedPtr < Other, RC, OtherRP > & ptr
);

### operator ==

bool operator == (
const SharedPtr & ptr
) const;

### operator ==

bool operator == (
const C * ptr
) const;

### operator ==

bool operator == (
C * ptr
) const;

### operator ==

bool operator == (
std::nullptr_t ptr
) const;

### operator >

bool operator > (
const SharedPtr & ptr
) const;

### operator >

bool operator > (
const C * ptr
) const;

### operator >

bool operator > (
C * ptr
) const;

### operator >=

bool operator >= (
const SharedPtr & ptr
) const;

### operator >=

bool operator >= (
const C * ptr
) const;

### operator >=

bool operator >= (
C * ptr
) const;

### operator C *

operator C * ();

### operator const C *

operator const C * () const;

### operator->

C * operator-> ();

### operator->

const C * operator-> () const;

### referenceCount

int referenceCount() const;

### reset

void reset();

### reset

void reset(
C * ptr
);

### reset

void reset(
const SharedPtr & ptr
);

### reset

template < class Other, class OtherRP > void reset(
const SharedPtr < Other, RC, OtherRP > & ptr
);

### swap

void swap(
SharedPtr & ptr
) noexcept;

### unsafeCast

template < class Other > SharedPtr < Other, RC, RP > unsafeCast() const;

Casts the SharedPtr via a static cast to the given type. Example: (assume class Sub: public Super)

    SharedPtr<Super> super(new Sub());
    SharedPtr<Sub> sub = super.unsafeCast<Sub>();
    poco_assert (sub.get());