This class implements IUnknown for a tear-off interface.

template
<class contained>
class CComCachedTearOffObject : public
    IUnknown,
public CComObjectRootEx<contained
::_ThreadModel::ThreadModelNoCS>

contained
Your tear-off class, derived from CComTearOffObjectBase and the interfaces you want your tear-off object to support.

CComCachedTearOffObject implements IUnknown for a tear-off interface. This class differs from CComTearOffObject in that CComCachedTearOffObject has its own IUnknown, separate from the owner object's IUnknown (the owner is the object for which the tear-off is being created). CComCachedTearOffObject maintains its own reference count on its IUnknown and deletes itself once its reference count is zero. However, if you query for any of its tear-off interfaces, the reference count of the owner object's IUnknown will be incremented.

If the CComCachedTearOffObject object implementing the tear-off is already instantiated, and the tear-off interface is queried for again, the same CComCachedTearOffObject object is reused. In contrast, if a tear-off interface implemented by a CComTearOffObject is again queried for through the owner object, another CComTearOffObject will be instantiated.

The owner class must implement FinalRelease and call Release on the cached IUnknown for the CComCachedTearOffObject, which will decrement its reference count. This will cause CComCachedTearOffObject's FinalRelease to be called and delete the tear-off.

CComObjectRootBase

CComObjectRootEx

IUnknown

CComCachedTearOffObject

Header: atlcom.h

Increments the reference count of the CComCachedTearOffObject object by 1.

STDMETHOD_(ULONG, AddRef)();

A value that may be useful for diagnostics and testing.

The constructor.

CComCachedTearOffObject(void* pv);

pv
[in] Pointer to the IUnknown of the CComCachedTearOffObject.

Initializes the CComContainedObject member, m_contained.

The destructor.

~CComCachedTearOffObject();

Frees all allocated resources and calls FinalRelease.

Calls m_contained::FinalConstruct to create m_contained, the CComContainedObject< contained> object used to access the interface implemented by your tear-off class.

HRESULT FinalConstruct();

A standard HRESULT value.

Calls m_contained::FinalRelease to free m_contained, the CComContainedObject< contained> object.

void FinalRelease();

A CComContainedObject object derived from your tear-off class.

CcomContainedObject <contained> m_contained;

contained
[in] Your tear-off class, derived from CComTearOffObjectBase and the interfaces you want your tear-off object to support.

The methods m_contained inherits are used to access the tear-off interface in your tear-off class through the cached tear-off object's QueryInterface, FinalConstruct, and FinalRelease.

Retrieves a pointer to the requested interface.

STDMETHOD(QueryInterface)(REFIID iid, void** ppvObject);

iid
[in] The GUID of the interface being requested.

ppvObject
[out] A pointer to the interface pointer identified by iid, or NULL if the interface is not found.

A standard HRESULT value.

If the requested interface is IUnknown, returns a pointer to the CComCachedTearOffObject's own IUnknown and increments the reference count. Otherwise, queries for the interface on your tear-off class using the InternalQueryInterface method inherited from CComObjectRootEx.

Decrements the reference count by 1 and, if the reference count is 0, deletes the CComCachedTearOffObject object.

STDMETHOD_(ULONG, Release)();

In non-debug builds, always returns 0. In debug builds, returns a value that may be useful for diagnostics or testing.

CComTearOffObject Class
CComObjectRootEx Class
Class Overview