Yeah, that's really badly worded. What it's trying to say is that if a Cocoa method has a NSError parameter, it will indicate error state by nil/NO return value

Yeah, that's really badly worded. What it's trying to say is that if a Cocoa method has a NSError parameter, it will indicate error state by nil/NO return value. It doesn't say anything about the value of the NSError if the return value is not nil/NO. So for example you could have the out parameter pointing at an existing NSError* at it's possible it will still point there if everything went ok.