A class definition can reference properties only when they are defined in the class or in one of its superclasses.

To reference a property of this class:

• Fix the code on the indicated line if the property has been defined in the class.

• Define the property in the class if the property has not been defined.

If you want to use the property in this class but you want subclasses to provide its implementation, declare it as an Abstract property in this class.