Class extension

“First, objects that are not instances of BNREmployee can no longer see this property. For instance, a
non-BNREmployee object could attempt to access an employee’s alarm code like this:
BNREmployee *mikey = [[BNREmployee alloc] init];
unsigned int mikeysCode = mikey.officeAlarmCode;

well, up to this point, the book is kind of inspiring. but at the begainning of this chapter the author leaves me totally in the sea!

[color=#FF0000]can you explain what do you mean by “a non-BNREmployee” object? In my opinion it mikey is a BNREmployee. :question: [/color]