Rick Parrish wrote:
>> 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;
>> }
>
> Short answer: yes that will work ... OR ... you could just declare aFile
> as type "nsILocalFile *" instead of a smart pointer and leave out the
> AddRef.
Generally, the latter is an undesirable pattern: it requires you to be
very careful with early returns due to error checking (which the above
function could really use, to avoid crashing when do_CreateInstance fails).
The cliché in the Mozilla source tree is:
nsresult rv;
nsCOMPtr<nsILocalFile> file = do_CreateInstance(..., &rv);
if (NS_FAILED(rv))
return rv;
*aNewFile = file;
NS_ADDREF(*aNewFile);
(``aFile'' would indicate the name of an argument -- really a parameter,
but hey -- so ``file'' is better for a local variable.)
Mike
