Base Classes and Derived Classes

• Base classes and derived classes
  • Object of one class "is an" object of another class
    • Example: Rectangle is quadrilateral.
      • Class Rectangle inherits from class Quadrilateral
      • Quadrilateral: base class
      • Rectangle: derived class
  • Base class typically represents larger set of objects than derived classes
    • Example:
      • Base class: Vehicle
        Cars, trucks, boats, bicycles, ...
      • Derived class: Car
        Smaller, more-specific subset of vehicles
• Inheritance examples (see Fig. 1)

  Figure 1: Inheritance examples

  
• Inheritance hierarchy (see Fig. 2 Top)
  • Inheritance relationships: tree-like hierarchy structure
  • Each class becomes
    • Base class; supply data/behaviors to other classes
    • OR
    • Derived class; inherit data/behaviors from other classes

  Figure 2: Inheritance hierarchy for university CommunityMembers and Inheritance hierarchy for Shapes

  

  
• public inheritance
  • Specify with:
  • Class TwoDimensionalShape : public Shape
    Class TwoDimensionalShape inherits from class Shape (see Fig. 2 Bottom)
  • Base class private members
    • Not accessible directly
    • Still inherited; manipulate through inherited member functions
  • Base class public and protected members; inherited with original member access
  • friend functions; not inherited