1. Abstract Classes & Object Slicing

2. Object Slicing

3. Assigning subtype to parent type variable slices the object Geometric Object Rectangle r1

4. Object Slicing Assigning subtype to parent type variable slices the object Geometric Object Rectangle r1 Geometric Object r2

5. Pointers/References Pointers / References don't slice – Just store memory address, don't have to

6. Casting No cast required to store child address in parent ptr: Virtual dispatch still finds child version of functions

7. Down Casting Can't auto convert parent pointer back to child one:

8. BAD static_cast, BAD static_cast happily pretends to turn a pointer into another pointer type… …weird stuff may happen

9. Static vs Dynamic Static : done at compile time Can this possibly make sense? Dynamic : done at runtime Try to see if this works…

10. Dynamic Cast dynamic_cast ( value ) – Type must be a pointer or reference – At runtime: Check to see if conversion makes sense If so, do it If not, return nullptr

11. dynamic_cast allows us to check if cast worked: GOOD dynamic_cast

12. dynamic_cast allows us to check if cast worked – Up to you to check! GOOD dynamic_cast

13. Abstract Functions

14. Geometric Object Example Circle Rectangle both have functions… should be in parent

15. Pure Virtual Functions Virtual Function : Child class may override, if working with pointer/reference, check to see if we have a better version

16. Pure Virtual Functions Pure Virtual Function : Child class MUST override this… I'm not even going to describe how it works "= 0 " This is pure virtual

17. New Problem… Can't make a GeometricObject:

18. Abstract Abstract Class : Class that is not designed to be instantiated – Defines common capabilities for subclasses GeometricObject +getArea() : double +getPerimeter() : double Italics = Abstract Class Italics = Abstract Method (Pure Virtual)

19. A Promise Abstract class is an organizer / promise

20. Using it We have no idea how each object will get its area, but we know it can:

21. Constructors Can't make a Geo object: Still need constructors for child classes

22. Protected Constructors Protected constructors make sure only usable from inside child classes GeometricObject +getArea() : double +getPerimeter() : double # = Protected