nsCOMPtr<nsISupportsString> obj = do_CreateInstance(NS_SUPPORTS_STRING_CONTRACTID, &status);
nsCOMPtr<nsISupportsString> obj = new nsSupportsStringImpl();
ExtractKeyString( nsHashKey* key, void*, void*, nsISupports** _retval )  /*    ...works with |nsHashtableEnumerator| to make the hash keys enumerable.  */{  nsresult status;  nsCOMPtr<nsISupportsString> obj = do_CreateInstance(NS_SUPPORTS_STRING_CONTRACTID, &status);  if ( obj ) {    nsCStringKey* strkey = NS_STATIC_CAST(nsCStringKey*, key);    status = obj->SetDataWithLength(strkey->GetStringLength(), strkey->GetString());  }  *_retval = obj;  NS_IF_ADDREF(*_retval);  return status;}