Messages not understood
Debugger messages stating <class or object> does not understand <message> are probably the most common errors. The causes include:
Misspelling the message selector
Sending the message to a class that does not support it
Sending the message to the wrong object
Passing the wrong number of arguments
Omitting a period or semicolon on the previous statement
Omitting or mismatching parentheses
Sending the message to an object that is nil
Implementing a class method as an instance method, or vice versa
Last modified date: 01/29/2015