1. Object Oriented Programming Key Features of OO Approach Data encapsulation –data and methods are contained in a single unit, object –promotes internal integrity –simplifies coding, debugging and maintenance Data hiding –no need to know all the details of implementation

2. Object Oriented Programming Key Features of OO Approach Inheritance –augment, restrict, specialize behavior –provides mechanism for reuse Polymorphism –different behavior of the same method or operator depending on the class and/or parameters

3. Object Oriented Programming What Is Design? Reiss: “design in the most general sense is an abstract description of how something is built” Design involves finding the set of alternatives most relevant to the problem, analyzing that set, and then choosing a subset of the alternatives that cooperatively solves the problem at hand in the “best” manner (making tradeoffs)

4. Object Oriented Programming Quality of Design Level of detail of components should be the same Number of components should be reasonable The hierarchy of components should be terminated at an appropriate level

5. Object Oriented Programming Object Oriented Decomposition Well-defined interfaces Cluster related objects

6. Object Oriented Programming Object a tangible self-contained entity that exhibits some well-defined behavior has state, behavior, and identity; the structure and behavior of similar objects are defined in their common class exists at run-time

7. Object Oriented Programming Class description of a number of similar objects – custom data type objects are instances of the class consists of interface and implementation provides three levels of access control –public, protected, private classes are related in various ways

8. #ifndef BANKACCOUNT_H #define BANKACCOUNT_H #include class BankAccount { private: string acctOwner; int acctNum; double curBalance; public: BankAccount(string, int); BankAccount(string, int, double); ~BankAccount() {}; void setBalance(double); double getBalance() const; }; #endif interface constructorsdestructormodifierselectorattributes

9. #include “bankacct.h” BankAccount::BankAccount(string name, int number) :acctOwner(name), acctNum(number),curBalance(0) { } BankAccount::BankAccount(string name, int number, double balance) : acctOwner(name), acctNum(number), curBalance(balance) { } void BankAccount::setBalance(double newBalance) {curBalance = newBalance); } double BankAccount::getBalance() const {return curBalance;} implementation initializing

10. using namespace std; #include “bankacct.h” void main() { BankAccount* ba = new BankAccount(“Jones”, 1234); ba->setBalance(200.00); cout getBalance()<<endl; delete ba; } use pointer deallocation

11. Object Oriented Programming Evaluation criteria for a design Correctness, completeness Simplicity Risk management Cohesion and coupling Information hiding Error handling

12. Object Oriented Programming Simplification Can operations be removed? Can data elements be removed? Can parameters be removed from operations? Can parameter and return types for operations be simplified? Are the operations and their parameters logically consistent?

13. Object Oriented Programming Simplify by making methods short Pseudocoding/coding guideline: a method should fit onto one page (one screen). If the method is too long, split it into separate methods. If there are too many methods in a class, rewrite a method so that it invokes lower-level classes.

14. Object Oriented Programming Cohesion and Coupling A class is cohesive if everything is directed toward a central purpose. A class has good coupling if it has minimal dependency on other classes. A class should not need to know the implementation of another class.

15. Object Oriented Programming Implementing OO design Two steps: –Convert class design into class declarations –Construct real code from pseudocode