lldb Error - no known method '-class'; cast the message send to the method's return type

p [[navigationController topViewController] class] 

returns

error: no known method '-class'; cast the message send to the method's return type 

To fix it, cast it first:- 

p [(NSObject *) [navigationController topViewController] class]

Refs
http://stackoverflow.com/questions/14007942/lldb-error-property-not-found-on-object-of-type