the Main properties of inheritance

Association of inheritance, such Internal-InternalChild called наследованием class in the Association — предок and the external потомок.

Basic properties of inheritance

  • When you inherit the attribute structure and composition of links is always increasing and can not be reduced (each inherited table stores все attributes всех ancestors).
  • The heir is available in the all attributes and associations of the ancestor. So, if we take an inner class InternalChild, its attributes will be Attr1 and Attr2, masters Master1, Master2, Master3, detaily Detail1, Detail2, Detail3, Detail4.
  • Ancestor provides polymorphic access to all his heirs, which means that the instance of the inner class and its heirs (in this case Internal and InternalChild) can be set as an instance of the artisan class (in this case Master2) and an instance of any heir of the master (in this case Master2Child). The situation is similar with detaylari: instance Internal equally through Detail2 operates with instances and Detail2 Detail2Child, and similarly for attributes and methods of the class. In practice, this phenomenon can cause the problem to be solved with the help of a typeusage](fo_type-usage-problem.html) that in a particular way is displayed in the data structure.
  • If the heir has the attribute method (with the same composition parameters), the Association (with the same role name), it means that the heir перегружает this element ancestor.
  • Heir from the master can be detailon the same inner class (as in a situation Internal-Master1-Detail4), that’s fine.
Переведено сервисом «Яндекс.Переводчик»