Getting "Undefined symbols" when trying to use EventKit?

I am trying to use EventKit based around the doco & SimpleEKDemo application, however I am getting the following single error.

What does this error mean and what开发者_运维百科 steps would be recommended for troubleshooting (first time I've had such a linking error & I'm a bit lost - I've parsed through my code versus teh example code and I can't see any obvious differences).

Undefined symbols:
  "_OBJC_CLASS_$_EKEventStore", referenced from:
      objc-class-ref-to-EKEventStore in AppointmentListController.o
ld: symbol(s) not found
collect2: ld returned 1 exit status

Note that in the header file from the controller I'm using the event kit code I do have:

#import <EventKit/EventKit.h>
#import <EventKitUI/EventKitUI.h>

Check if you have added EventKit and EventKitUI frameworks to link with your target?

You might be forgot any of below things

1. add eventKitFramwork in Your project
2. Import this framework in your file #import