How to convert wchar_t to NSString?

I have wchar_t buffer [100] . Sometimes it needed for Unicode letters, sometimes is not.

I need to convert it to NSString.

I'm using NSString *str = [NSString string:(char *)buffer]; to conver it.

When I'm trying to NSLog my NSString, sometimes it getting right result, but sometimes is not.

Did I miss something?

Thanks!