1. Chapter 25
GRASP
The other four

2. GRASP
Polymorphism
Indirection
Pure Fabrication
Protected Variations

3. Polymorphism Handle alternatives based on type
Simplify methods by removing cases

4. Fig. 25.1

5. Implementation in Monoploy

6. Fig. 25.2

7. Fig. 25.3

8. Fig Go Square

9. Fig Regular Square

10. Fig Income Tax

11. Fig Goto Jail

12. Improving coupling Piece knows square, player does not
Therefore player needs to use piece too often
Refactor

13. Interfaces
Choosing interfaces vs polymorhism

14. Pure Fabrication
Assign a responsibility to avoid violations of High Cohesion and Low Coupling
Make up an object to assign a highly cohesive set of responsibilities

15. Example: Databases and Sale
Saving to database requires:
DB Task requires a large number of support operations, unrelated to main class
Sale Class has to be coupled to db connector
Saving in DB is a general task using many support classes
Fabricate DB persistence object

16. Dice in Monopoly Dice can be more general that just in monopoly
Some games have a dice cup

17. Fig. 25.8

18. Fig. 25.9

19. Design of objects Representaional decomposition
Behavioral decomposition

20. Indirection
Avoid direct coupling

21. Fig

22. Persistent Storage
Often a good use of indirection

23. Protected Variations
Design for object, subsystems or systems to reduce instability
Identify predicated points of variation
Create a stable interface
Similar to indirection
Hide structure and information

24. Summary