CoCreateInstance function (combaseapi.h)

Makale
10/18/2021

Creates and default-initializes a single object of the class associated with a specified CLSID.

Call CoCreateInstance when you want to create only one object on the local system. To create a single object on a remote system, call the CoCreateInstanceEx function. To create multiple objects based on a single CLSID, call the CoGetClassObject function.

Syntax

HRESULT CoCreateInstance(
  [in]  REFCLSID  rclsid,
  [in]  LPUNKNOWN pUnkOuter,
  [in]  DWORD     dwClsContext,
  [in]  REFIID    riid,
  [out] LPVOID    *ppv
);

Parameters

[in] rclsid

The CLSID associated with the data and code that will be used to create the object.

[in] pUnkOuter

If NULL, indicates that the object is not being created as part of an aggregate. If non-NULL, pointer to the aggregate object's IUnknown interface (the controlling IUnknown).

[in] dwClsContext

Context in which the code that manages the newly created object will run. The values are taken from the enumeration CLSCTX.

[in] riid

A reference to the identifier of the interface to be used to communicate with the object.

[out] ppv

Address of pointer variable that receives the interface pointer requested in riid. Upon successful return, *ppv contains the requested interface pointer. Upon failure, *ppv contains NULL.

Return value

This function can return the following values.

Return code	Description
S_OK	An instance of the specified object class was successfully created.
REGDB_E_CLASSNOTREG	A specified class is not registered in the registration database. Also can indicate that the type of server you requested in the CLSCTX enumeration is not registered or the values for the server types in the registry are corrupt.
CLASS_E_NOAGGREGATION	This class cannot be created as part of an aggregate.
E_NOINTERFACE	The specified class does not implement the requested interface, or the controlling IUnknown does not expose the requested interface.
E_POINTER	The ppv parameter is NULL.

Remarks

The CoCreateInstance function provides a convenient shortcut by connecting to the class object associated with the specified CLSID, creating a default-initialized instance, and releasing the class object. As such, it encapsulates the following functionality:

CoGetClassObject(rclsid, dwClsContext, NULL, IID_IClassFactory, &pCF); 
hresult = pCF->CreateInstance(pUnkOuter, riid, ppvObj);
pCF->Release();

It is convenient to use CoCreateInstance when you need to create only a single instance of an object on the local machine. If you are creating an instance on remote computer, call CoCreateInstanceEx. When you are creating multiple instances, it is more efficient to obtain a pointer to the class object's IClassFactory interface and use its methods as needed. In the latter case, you should use the CoGetClassObject function.

In the CLSCTX enumeration, you can specify the type of server used to manage the object. The constants can be CLSCTX_INPROC_SERVER, CLSCTX_INPROC_HANDLER, CLSCTX_LOCAL_SERVER, CLSCTX_REMOTE_SERVER or any combination of these values. The constant CLSCTX_ALL is defined as the combination of all four. For more information about the use of one or a combination of these constants, see CLSCTX.

UWP applications

Although there are no restrictions on which CLSIDs a UWP application can pass to CoCreateInstance, many objects will fail with E_ACCESSDENIED for security reasons, especially if they do not run in-process. Additionally, even if you can successfully create an object, it might fail at a later time due to UWP security constraints, app-model differences, etc. In particular, background tasks should limit the objects they communicate with to avoid hangs or other complications due to connected stand-by.

Examples

// Create WIC factory
hr = CoCreateInstance(
    CLSID_WICImagingFactory,
    NULL,
    CLSCTX_INPROC_SERVER,
    IID_PPV_ARGS(&m_pIWICFactory)
    );

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	combaseapi.h (include Objbase.h)
Library	Ole32.lib
DLL	Ole32.dll

Aracılığıyla paylaş