IEnumFORMATETC:IUnknown
This interface is used to enumerate an array of FORMATETC structures. IEnumFORMATETC has the same methods as all enumerator interfaces: Next, Skip, Reset, and Clone.
When to Implement
IEnumFORMATETC must be implemented by all data objects to support calls to the IDataObject::EnumFormatEtc method, which supplies a pointer to the enumerator's IEnumFORMATETC interface. If the data object supports a different set of FORMATETC information depending on the direction of the data (whether a call is intended for the SetData or GetData method of IDataObject), the implementation of IEnumFORMATETC must be able to operate on both.
The order of formats enumerated through the IEnumFORMATETC object should be the same as the order that the formats would be in when placed on the Clipboard. Typically, this order starts with private data formats and ends with presentation formats, such as CF_METAFILEPICT.
When to Use
Call the methods of IEnumFORMATETC when you need to enumerate the FORMATETC structures defining the formats and media supported by a given data object. This is necessary in most data transfer operations, such as Clipboard and drag-and-drop, so the object on the other end of the data transfer can determine whether the appropriate format and media for the data is supported.
Note To Implementers
If the IEnumFORMATETC::Next method returns a non-NULL DVTARGETDEVICE pointer in the ptd member of the FORMATETC structure, it must be allocated with the CoTaskMemAlloc function (or its equivalent).
Note to Callers
If the IEnumFORMATETC::Next method returns a non-NULL DVTARGETDEVICE pointer in the ptd member of the FORMATETC structure, the memory must be freed with the CoTaskMemFree function (or its equivalent). Failure to do so will result in a memory leak.
Methods
The following table shows the methods for this interface in alphabetical order.
| IEnumFORMATETC method | Description |
|---|---|
| Clone | Creates another enumerator that contains the same enumeration state as the current enumerator. |
| Next | Retrieves the next celt items in the enumeration sequence. |
| Reset | Resets the enumeration sequence to the beginning. |
| Skip | Skips over the next specified number of elements in the enumeration sequence. |
Remarks
To determine whether the platform supports this interface, see Determining Supported COM APIs.
Requirements
OS Versions: Windows CE 3.0 and later.
Header: Objidl.h, Objidl.idl.
Link Library: Ole32.lib, Uuid.lib.
See Also
CoTaskMemAlloc | CoTaskMemFree | IDataObject | IDataObject::EnumFormatEtc | FORMATETC
Last updated on Wednesday, April 13, 2005
© 2005 Microsoft Corporation. All rights reserved.