Hello,

latest stable branch of the client library, version 1.4.x compatible with serve 6.x, provides alternative methods that include an NSError as the last argument. I.e.

- (LSSubscribedTableKey *) subscribeTableWithExtendedInfo: (LSExtendedTableInfo *)tableInfo delegate: (id <LSTableDelegate>)delegate useCommandLogic: (BOOL)commandLogic error: (NSError * __autoreleasing *)error;

From Swift 2.0 it appears as a throws method. It is included with the latest server distribution.
Note: it is not compatible with server version 5.x and earlier.

Alternatively, we are working on a Unified Client API version of the client library, currently in alpha, that throws no such exceptions but rather delivers them asynchronously via the subscription delegate. It is available on CocoaPods, or you may find direct download links on the blog post introducing the new library.
Note: it is not compatible too with server version 5.x and earlier. Moreover, the APIs change substantially.

Hope this helps. Best regards,

Gianluca