CComClassFactorySingleton Class
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This class derives from CComClassFactory and uses CComObjectGlobal to construct a single object.
Important
This class and its members cannot be used in applications that execute in the Windows Runtime.
Syntax
template<class T>
class CComClassFactorySingleton : public CComClassFactory
Parameters
T
Your class.
CComClassFactorySingleton derives from CComClassFactory and uses CComObjectGlobal to construct a single object. Each call to the CreateInstance method simply queries this object for an interface pointer.
Members
Public Methods
| Name | Description |
|---|---|
| CComClassFactorySingleton::CreateInstance | Queries m_spObj for an interface pointer. |
Public Data Members
| Name | Description |
|---|---|
| CComClassFactorySingleton::m_spObj | The CComObjectGlobal object constructed by CComClassFactorySingleton. |
Remarks
ATL objects normally acquire a class factory by deriving from CComCoClass. This class includes the macro DECLARE_CLASSFACTORY, which declares CComClassFactory as the default class factory. To use CComClassFactorySingleton, specify the DECLARE_CLASSFACTORY_SINGLETON macro in your object's class definition. For example:
class ATL_NO_VTABLE CMySingletonClass :
public CComObjectRootEx<CComSingleThreadModel>,
public CComCoClass<CMySingletonClass, &CLSID_MySingletonClass>,
public IMySingletonClass
{
public:
DECLARE_CLASSFACTORY_SINGLETON(CMySingletonClass)
// Remainder of class declaration omitted.
Inheritance Hierarchy
CComObjectRootBase
IClassFactory
CComClassFactorySingleton
Requirements
Header: atlcom.h
CComClassFactorySingleton::CreateInstance
Calls QueryInterface through m_spObj to retrieve an interface pointer.
STDMETHOD(CreateInstance)(LPUNKNOWN pUnkOuter, REFIID riid, void** ppvObj);
Parameters
pUnkOuter
[in] If the object is being created as part of an aggregate, then pUnkOuter must be the outer unknown. Otherwise, pUnkOuter must be NULL.
riid
[in] The IID of the requested interface. If pUnkOuter is non- NULL, riid must be IID_IUnknown.
ppvObj
[out] A pointer to the interface pointer identified by riid. If the object does not support this interface, ppvObj is set to NULL.
Return Value
A standard HRESULT value.
CComClassFactorySingleton::m_spObj
The CComObjectGlobal object constructed by CComClassFactorySingleton.
CComPtr<IUnknown> m_spObj;
Remarks
Each call to the CreateInstance method simply queries this object for an interface pointer.
Note that the current form of m_spObj presents a breaking change from the way that CComClassFactorySingleton worked in previous versions of ATL. In previous versions the CComClassFactorySingleton object was created at the same time as the class factory, during server initialization. In Visual C++.NET 2003, the object is created lazily, on the first request. This change could cause errors in programs that rely on early initialization.
See Also
IClassFactory
CComClassFactory2 Class
CComClassFactoryAutoThread Class
CComObjectRootEx Class
CComGlobalsThreadModel
Class Overview