xpcom beginner question

[Eremia A]

Hi...
I'm a beginner to xpcom and I'd like to know the answer to some basic
questions.

1. Here "somefunction" is a getter function.

NS_IMETHODIMP SomeClass::somefunction( nsILocalFile ** aNewFile ) {
  nsresult rv;
  nsCOMPtr<nsILocalFile> aFile =
o_CreateInstance( NS_LOCAL_FILE_CONTRACTID, &rv );
  aFile->InitWithPath( "/some/path/file" );

  *aNewFile = aFile;

  return NS_OK;
  }

nsCOMPtr<nsILocalFile> file;
foo->somefunction( getter_AddRefs( file ) );
After calling "somefunction", file was a bad pointer, because the aFile was
created inside the function and then deleted at the return from
"somefunction".


Is this example below the right way to fix the problem?

NS_IMETHODIMP SomeClass::somefunction( nsILocalFile ** aNewFile ) {
  nsresult rv;
  nsCOMPtr<nsILocalFile> aFile =
o_CreateInstance( NS_LOCAL_FILE_CONTRACTID, &rv );
  aFile->InitWithPath( "/some/path/file" );

  nsILocalFile *dummy = aFile;
  NS_ADDREF( dummy );

  *aNewFile = dummy;

  return NS_OK;
  }

2. I created a nsMyWebProgressListener class, derived from
nsIWebProgressListener. The nsMyWebProgressListener  is used locally, it
doesn't have to have a CID or IID. I need to pass a
nsIWebProgressListener*    to "SetWebProgressListener".
Is there something wrong to code it this way?

nsCOMPtr<nsIWebProgressListener> dummy = new nsMyWebProgressListener;
aLauncher->SetWebProgressListener( dummy );

Thanks.