I'm following the guide from developer.apple.com to implement a PreferencePane. I create a cocoa bundle project, and add the PreferencePanes framework. And then, I create a class MyPreferencePane inheriting class NSPreferencePane. It's strange that there's no prompt from the code sense when I type NSPreferencePane. So, I guess there're some problem happened. When I compile the project, there occur four errors: 1) NSPreferencePane.h:No such file or directory 2) Can't find interface declaration for 'NSPreferencePane' Both of the above errors occured twice. These errors seem invoked by no PreferencePane class found. But I have added PerferencePanes framework. How can these errors happen? I'm so puzzled.