Step Seven: Implement the IPersistFile Interface

To implement the IPersistFile interface, the file viewer must implement the following member functions: GetClassID, Load, GetCurFile, IsDirty, Save, and SaveCompleted.

GetClassID

This function returns the document's CLSID.

STDMETHODIMP CFileView::XPersistFile::GetClassID (LPCLSID
pClsID)

{

METHOD_PROLOGUE (CFileView, PersistFile);



*pClsID = pThis->m_clsID;

return NOERROR;

}

Load

This function loads the document contained in the given filename. Load only stores the filename; ShowInitialize actually opens the file.

STDMETHODIMP CFileView::XPersistFile::Load (

LPCOLESTR pszFileName, DWORD dwMode)

{

METHOD_PROLOGUE (CFileView, PersistFile);



// No modifications are necessary to this code; it simply

// copies the parameters into the CFileView::m_pszPath and

// m_grfMode members for use in IFileViewer::ShowInitialize

// and IFileViewer::Show later on.



// You should never be called twice.

if (pThis->m_pszPath)

pThis->m_fLoadCalled = FALSE; // handle error case



if (pszFileName == NULL)

return E_INVALIDARG;



// Copy the ANSI filename and the mode to use in opening it.

lstrcpy (pThis->m_pszPath, pszFileName);



// Remember that this function has been called.

pThis->m_fLoadCalled = TRUE;

return NOERROR;

}

GetCurFile

This function returns either the absolute path of the document's currently associated file or the default filename prompt if there is no currently associated file. GetCurFile returns E_UNEXPECTED if the Load function has not yet been called; otherwise, it copies the path and returns NOERROR.

STDMETHODIMP CFileView::XPersistFile::GetCurFile (

LPOLESTR __RPC_FAR *ppszFileName)

{

LPOLESTR psz;

ULONG cb;



METHOD_PROLOGUE (CFileView, PersistFile);



// No modifications are necessary to this code; it simply

// copies the CFileView::m_pszPath string into a piece

// of memory and stores the pointer at *ppszFile.



// Load must be called, of course.

if (pThis->m_fLoadCalled)

return E_UNEXPECTED;



if (ppszFileName == NULL)

return E_INVALIDARG;



cb = (lstrlen (pThis->m_pszPath) + 1) * sizeof (OLECHAR);

psz = (LPOLESTR) malloc (cb);



if (NULL == psz)

return E_OUTOFMEMORY;



return NOERROR;

}

IsDirty

This function checks a document object for changes that might have been made since the object was last saved. IsDirty can simply return S_FALSE because a file viewer does not modify the file.

STDMETHODIMP CFileView::XPersistFile::IsDirty (void)

{

return S_FALSE;

}

Save

The Save function saves a copy of the object to the specified filename. Both the Save and the SaveCompleted member functions should return E_NOTIMPL.

STDMETHODIMP CFileView::XPersistFile::Save (

LPCOLESTR pszFileName, BOOL fRemember)

{

return E_NOTIMPL;

}

SaveCompleted

This function signals that the caller has saved the file with a call to IPersistFile::Save and has finished working with it.

STDMETHODIMP CFileView::XPersistFile::SaveCompleted (

LPCOLESTR pszFileName)

{

return E_NOTIMPL;

}