1. Ch4: Software Architecture and Design

2. 1 Categories of classes Data Managers: class Item { private: // Private Data int UPC; char* Name; int InStock, OnShelf, ROLimit; float RetailCost; public: // Public Methods Item(int code, char* str, int st1, int st2, int st3, float cost); void CreateNewItem(); int GetUPC(); char* GetName(); int GetQuantity(); int CheckReorderStatus(); void PrintItem(); void UpdatePrice(float new_value); };

3. 2 Categories of classes (contd..) class ItemDB {private: int Num_Items; int Curr_Item; Item* AllItems[Max_Items]; int FindFirstItem(); int FindNextItem(); int FindItemUPC(int code); int FindItemName(char* name); public: ItemDB(); // Constructor void InsertNewItem(Item* new_one); void DeleteExistingItem(int code); void FindDisplayItemUPC(int code); void FindDisplayItemName(char* name); void PrintAllItems(); }; Data sinks/data sources:

4. 3 Categories of classes (contd..) I1 “milk” I2 “peas” I3 “soda” ItemDB Data Manager class Data Source/Sink class Data Source/Sink class is added for implementation.

5. 4 Categories of classes (contd..) View/Observer: Provide an interface for user - class InvControlGUI { private: int Curr_Option; // Current menu option public: InvControl(); // Constructor void PrintMenuSetOption(); void ActivateController(); void EnterNewItem(); void RemoveExistingItem(); void FindItem(); void InvSearchQuantity(); void InvSearchReorder(); void GenerateAnOrder(); };

6. 5 Categories of classes (contd..)  Facilitator/Helper – Used to support complex tasks  For HTSS, Facilitator/Helpers are as follows:

7. 6 Common design flaws  Classes that directly modify the private data of other classes  E.g. class Item from HTSS  Change RetailCost via UpdatePrice()  Do not access RetailCost directly class Item { private: // Private Data float RetailCost; public: // Public Methods void UpdatePrice(float new_value); };

8. 7 Common design flaws (contd..)  Too much functionality in one class class Item { protected: // Attributes as given in earlier examples public: // Two constructors for versatility int GetUPC(); char* GetName(); int GetInstockAmt(); int GetOnShelfAmt(); int GetQuantity(); int GetReorderAmt(); float GetRetailPrice(); float GetWholeSaleCost(); void UpdateName(char* item_name); void UpdateInstockAmt(int stock_amt); void UpdateOnShelfAmt(int shelf_amt); void UpdateReorderAmt(int reord_amt); void UpdateRetailPrice(float price); void UpdateWholeSaleCost(float wholesale); } void PrintUPCName(); void PrintNamePrice(); void PrintInventory(); void PrintProfitInfo(); void PrintUPC(); void PrintName(); void PrintInstockAmt(); void PrintOnShelfAmt();

9. 8 Common design flaws (contd..)  A class that lacks functionality:  Classes that have unused functionality  Classes that duplicate functionality

10. 9 Common design flaws (contd..)  What’s in a name?  Remember, somebody else who comes after you has to understand and maintain what you develop!

11. 10 Inheritance: Motivation  Consider a software application written for a university  Four types of individuals and their attributes have been identified: Faculty Dean UnderGrad Grad Name Name Name Name SSN SSN SSN SSN Rank School Dorm Dorm Dept Dept Year Program Yrs Yrs GPA Degree GPA  To successfully utilize inheritance:

12. 11 Inheritance: Motivation Person Faculty: Person Dean:Person Name Rank School SSN Dept. Dept. Years Years Undergrad: Person Grad: Person Dorm Dorm Year Program GPA Degree GPA Person Faculty Dean Undergrad Grad

13. 12 Inheritance: Motivation Person Name SSN Employee Student Dept. Dorm Yrs. GPA Faculty Dean Undergrad Grad Rank School Year Program Degree

14. 13 Inheritance: Motivation Person Name SSN Employee Student Dept. Dorm Yrs. GPA Faculty Dean Undergrad Grad Rank School Year Program Degree

15. 14 Inheritance: Definition  What is inheritance?  Generalization and specialization:  Subclass is more refined than superclass – its specialized  Superclass contains common characteristics of its subclasses – its generalized

16. 15 Inheritance: Definition  When can inheritance be used?  Inheritance permits reuse:

17. 16 Role of inheritance  Develop inheritance hierarchies that are:  Utilization of inheritance: How  Benefits of inheritance: Why  Impact of inheritance: Cost

18. 17 Benefits of inheritance  Software reusability  Design and code sharing

19. 18 Benefits of inheritance (contd..)  Software components  Rapid prototyping  All benefits apply to design, development and maintenance

20. 19 Cost of inheritance  Execution speed:  Gen. purpose solution, not faster.  Program size:  Large libraries, but memory size not a factor.  Platform independence (Java) impacts both speed and size.

21. 20 Cost of inheritance (contd..)  Message passing overhead:  Search class, parent, grandparent etc. for the right method.  Program complexity:  Train SEs.  CFG understanding may need multiple scans up/down.

22. 21 Specialization and generalization inheritance  Specialization:  Generalization  General parent class customized to include more data, more methods or both.  Child class special case of parent class.  Good form of inheritance.

23. 22 Specialization and generalization inheritance - Example class PItem : public Item { protected: food_state Environ; int Days; void ItemSpecificPrint(); public: virtual void CreateNewItem(); virtual void PrintItem(); virtual void PrintPerish(); virtual void UpdateItem(); void PrintDaysFoodState(); }; class DeliItem : public PItem {protected: float Weight; float CostPerLb; void ItemSpecificPrint(); public: virtual void CreateNewItem(); virtual void PrintItem(); virtual void PrintPerish(); virtual void UpdateItem(); void PrintWeightandCost(); }; Item / \ NonPItem PerishItem / \ \ DeliItem DairyItem ProduceItem Generalization Specialization Food state: shelf, expiration data Weight & cost: