IActiveDesigner::QueryPersistenceInterface

Asks about the persistence interface implemented by the run-time object.

HRESULT QueryPersistenceInterface(
REFIID riid
);

Parameter

riid

[in] Identifier of a persistence interface. Possible values are as follows:

Interface Identifier

Meaning

IID_IPersistFile

File persistence.

IID_IPersistStorage

Storage persistence.

IID_IPersistStream

Stream persistence.

IID_IPersistStreamInit

Stream persistence with initialization.


Return Values

The return value obtained from HRESULT is one of the following:

Return Value

Meaning

S_OK

The designer supports the specified persistence interface.

S_FALSE

The designer does not support the interface.

E_FAIL

The method failed for an unknown reason.

E_INVALIDARG

The argument is invalid.

E_NOTIMPL

The design-time and run-time objects are the same.

E_OUTOFMEMORY

Out of memory.


Comments

The persistence interface requested depends on the host; different hosts will request different interfaces. Visual Basic 5.0, for example, does not use file persistence.

The host uses this method together with the SaveRuntimeState method to save persistent data needed later to create and load the run-time object. It asks the visual designer for persistence interfaces in order of preference.

Example

The following example implements QueryPersistenceInterface for an ActiveX designer that supports three persistence interfaces:

STDMETHODIMP CMyDesigner::QueryPersistenceInterface
(
    REFIID riid
)
{
        if (riid == IID_IPersistStreamInit)
                return S_OK;
        else if (riid == IID_IPersistStorage)
                return S_OK;
        else if (riid == IID_IPersistStream)
                return S_OK;
        else 
                return S_FALSE;
}