Nitty Gritty

• Protected members
  • All public members are availble to derived classes.
  • All protected members are avialble to all derived classes, but not to non-class members.
  • All private members are only accessable by the base class, not derived classes.
  • See page 202
  • Meyers does not like protected.
• Member Access in declaration of inheritence
  • See page 331
  • Meyers has disane for protected inheritance " and protected inheritance is something whose meaning eludes me to this day." (Effective C++, page 151)
  • Meyers devotes an entire item to private.
    • He devotes an entire section to this.
    • But he sasys to avoid it.

  • class a: public b {};
    class a: protected b {};
    class a: private b {}; 

  • Public: all members are inherited as described above
  • Protected: all public members of the base class become protected in the derived class.
  • Private : all public and protected members of the base class become private members of the derived class.
    • This is weird, see private.cpp
• You can stop inheritence with the keyword final

  • class DeadEnd final{};
    class class Base {};
    class SecondEnd: public Base final {}; 

• Virtual Methods
  • So far, we have hidden methods.
  • By using the keyword virtual you can override methods properly.
  • This is the gateway to true polymorphism.
• In the prevous example
  • Produce was not declared virtual

  • class BuildingT {
        public:
            BuildingT(WarehouseT w, BuildingTypeT t);
            ...
            void Produce(WarehouseT w); 

  • And so

        genericBuilding = make_unique<FarmT>(warehouse);
        genericBuilding->CanProduce(warehouse);
        genericBuilding->Produce(warehouse); 

  • produced

  • In the FarmT class, building a farm
    Base class checking to see if we can produce
    Base class producing 

  • In the new example Produce is declared virtual

  • class BuildingT {
        public:
            BuildingT(WarehouseT w, BuildingTypeT t);
            ...
            virtual void Produce(WarehouseT w); 

  • So the code produces

  • In the FarmT class, building a farm
    Base class checking to see if we can produce
    A Farm is producing