2. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 DCO10105 Object-Oriented Programming and Design  Lecture 6: More on class construction UML and an introduction to inheritance  More on class construction Multiple inclusion Use of accessor and mutator Function overload and signature Members of pointer The resolution operator :: and namespace  UML and an introduction to inheritance UML: Class diagram Some class diagrams in the real world Some class diagrams for typical applications -- By Rossella Lau

3. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 #inndef _INT_ARRAY_H #define _INT_ARRAY_H...... #endif  These are pre-processor statements to avoid multiple inclusion  The pre-processor uses a symbol _INT_ARRAY_H to indicate that the body within #inndef -- #endif, including _INT_ARRAY_H, will be defined if it is not defined yet  When the same header file is included the second time, since it is already defined, the body will not be included Revisit IntArray.h & IntArray.cpp

4. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 The dynamic array -- pointer  The dynamic array *array actually is a pointer  Its main purpose is to get dynamic memory allocation for the array  However, whenever you have a pointer variable, it complicates the constructors and destructors and usually you must define your own rather than using those generated by the compiler  In other words, for simple classes such as clockType and Qudratic, we can use the compiler generated constructors and destructors

5. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 The identifier starting with _  Identifiers of data members in IntArray start with _ (an underscore)  Traditionally, C defines system (library functions) variables with a prefix “_” to avoid conflict with programmer defined variable names

6. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Use of accessor and mutator  Although a member can access any other members in a class, it is a good habit to use accessor and mutator in service functions and use mutator to set the value for the data in the constructor if the respective data does have a domain checking and maintaining in the mutator; e.g., DateType.cpp  I.e., Data members are usually only directly referenced in constructors, accessors, and mutators; recheck: IntArray.cpp & Quadratic.cpp

7. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Function overload  Several constructor ids and identical function ids can exist in the same class or the same program  IntArray(int), IntArray(IntArray const &)  fillData(double[],size_t), fillData(int[],size_t)  Same function ids with different signatures are allowed in modern languages  Return type & parameters of a function are the function’s signature  When a function call is encountered, the compiler checks the type(s) of its parameter(s), the signature, and finds the function with such signature to call

8. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 :: and namespace  :: identifies a member of a class (. identifies a member of an object)  :: can also identify members in namespace  Namespace: Malik’s slide: 8:18-23  Same symbol but different application  You cannot use “using namespace IntArray” to save the typing of “IntArray::” for the function implementation in IntArray.cpp

9. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 UML  Unified Modeling Language  Software blueprint language  Similar to blueprints, standard graphical language, for the architects and builders  There are nine kinds of modeling diagrams:  Use Case diagrams, Class diagrams, Object diagrams, Sequence diagrams, Collaboration diagrams, Statechart diagrams, Activity diagrams, Component diagrams, and Deployment diagrams  Reference: www.borland.com

10. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Class diagram  It gives an overview of a system by showing the relationships among them  Association: relationship between instances of two classes It is a link in a diagram  Aggregation: an association in which one class belongs to a collection It is a link with a diamond end pointing to the part containing the whole  Generation: indicating inheritance between classes It is a link with a triangle end pointing to the base class from sub classes

11. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Navigation and multiplicity  In the above class diagram, it uses navigability arrow to represent the relationship rather than the standard  It shows which direction the association can be traversed  Multiplicity shows the possible instances for an aggregation; e.g.,  An order has at least one order item  A catalog has zero or many products

12. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 An example: customer orders  http://bdn.borland.com/article/0,1410,31863,00.html#classdiagrams

13. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Class notation  A 3-piece rectangle: E.g., Malik’s Figure 12-1 Class name Attributes Operations

14. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Visibility and scope  http://bdn.borland.com/article/images/31863/classdiagram.html

15. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Introduction to inheritance  A sub class has the attributes and properties (operations) of its base class  A sub class inherits everything from its base class in OO view: all the data members and function members  It is quite similar to class taxonomy or class classification in the real world Animals can be classified as: mammal, bird, fish; there are different kinds of mammals: man, pet, wild animal, farm animal, whale, etc

16. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Real world example : CityU

17. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Real world example : Animal

18. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Application: The shapes

19. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Application: Course management

20. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 A class diagram for gourmetCoffee

21. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Other typical applications  A restaurant system  A retail system  A course management system  A library system  A payroll system

22. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Summary  In this class, we revisited class construction with some related concepts and techniques: pre-processor’s supports, pointer member and class, good programming practice in using accessor and mutator, and :: & namespace  The class diagram of the UML helps in modeling a system  The class diagram also introduces the relationship of inheritance

23. Rossella Lau Lecture 6, DCO10105, Semester B,2005-6 Reference  Malik: 8.3, 12.1.1, 13  http://bdn.borland.com/article/0,1410,31863,00.html -- END --