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Asked: 2026-05-11T09:36:38+00:00

When do you use each inheritance? class Base{}; class Derived: protected Base{}; class Derived2:

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When do you use each inheritance?

class Base{};  class Derived: protected Base{}; class Derived2: public Base{};

My case:

I have class called Snapshot which only contains GetXXX methods. It is a light-weight classed used to store current state of the Value class. I also use it for recovery, keeping instances of this class long after Value class instance are gone. A Manager class, processes instances of the Snapshot class. Let me show you the code:

class Snapshot {         public:             Snapshot (const Snapshot * snap)             {               _x=snap->_x;                  _y=snap->_y;                 _z=snap->_z;               }             Snapshot (){_x=_y=_z=0;}             int GetX(){return _x;}             int GetY(){return _y;}             int GetZ(){return _z;}             ~virtual Snapshot(){}            protected:               int _x,_y,_z;                };  class Value:public Snapshot  {   /*Very heavy class with a lot of components used to calculate _x, _y, _z*/   };   class Manager {        public:          void Process( const Snapshot * snap)          {           }   };

How do you feel about this design? What are the alternatives?

Thanks

Solutions and issues

  • Solution: I would create makeSnapshot function which would return Snapshot object by given Value object.

  • Issues:

    • major issue: I sent snapshots at very frequently (every second, even less), hence I don’t want to incur the construction and destruction cost minor issue:

    • semi-major issue I will have to make Value a friend of Snapshot, as I don’t want
      to introduce setters.

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1 Answer

  1. Generally speaking I would use public inheritance, if I want to implement a specific interface, e.g. if my class is to be accessed thrugh a specific contract. Protected inheritance could be used, if you just want to reuse the functionality implemented in the parent.

    I would make Snapshot a pure virtual class, e.g. just an interface, and Value would implement the getXYZ methods. E.g. you probably don’t need the _x,_y,_z members in Snapshot.

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