COP330 Object Oriented Programming in C++ Fall 2008

1. COP330Object Oriented Programming in C++Fall 2008 Dr. David A. Gaitros dgaitros@admin.fsu.edu

2. Introduction to Object Oriented Programming (OOP) • OOP combines the data and functions that manipulate the data into a single package called objects. • Data – The object’s attributes • Functions – The object’s behavior • The “Packages” have the favorable Software Engineering property of Information Hiding • Objects know how to communicate with each other via well-defined interfaces • Implementation details are hidden

3. Introduction to Object Oriented Programming (OOP) • C++ is a language that allows you to program using the OOP style. • You can program in C++ using non-OOP styles. • In OOP the unit of programming is called a class. • An object is an item that is an instantiation (actually define a variable ) of a class. • Remember that a class has both data and functions combined.

4. Introduction to Object Oriented Programming (OOP) • C++ Classes • A programmer creates their own user-defined types called classes. • Classes do not set aside storage or define variables. They only tell the compiler what a class looks like. • These are also called programmer-defined types. • Each class contains data and functions to manipulate the data • Data components of a class are called data members. • Function are called member functions. • An instance of a user-defined type is called an object.

5. Introduction to Object Oriented Programming (OOP) • Remember that the C language is a proper subset of the C++ language. So you can take a C program and give it to a C++ compiler and it will compile fine. • You can actually do OOP style in the C language but it is more difficult because of the lack of definition of a class. We use C “struct” concepts.

6. Introduction to Object Oriented Programming (OOP) • C “Struct” Struct Time { int hour; int minute; int second; }; Time Todays_Time; Time Time_Array[10];

7. Introduction to Object Oriented Programming (OOP) • So what is the difference: • In C, Data and functions are always separate • In C++, you can build objects that have both the data and functions put together. C++ Libraries can contain useful classes that store data in useful and reusable ways. Classes then become the building blocks for more complex programs.

8. Introduction to Object Oriented Programming (OOP) • There are three parts in a C++ program related to objects: • DDU • Declare: Define the types of data that will be used, give them names, declare the functions and their interface. • Define: Put the details into the class. Write the code and the implementation details. • Use: The actual code that uses the class.

9. Introduction to Object Oriented Programming (OOP) • Protected levels in a class: • Public: Can be accessed both within and external to the object. • Private: Can only be used by the object itself. • The public section of a class is usually called the interface. It is what the programmers sees. • Normally, All data is private and only the bare essential functions are made public.

10. Introduction to Object Oriented Programming (OOP) • Reason’s for hiding • Reduces complexity much like the detailed workings of an automobile are hidden from the average driver. • Principle of least privilege (need-to-know) • More Secure. Less likely that someone will alter or misuse something. • Easier to change the implementation without affecting other modules that use it.

11. Introduction to Object Oriented Programming (OOP) class <className> { public: // public data // public functions private: // private data // private functions };

12. Introduction to Object Oriented Programming (OOP) • Example of a Definition of a class TimeType class TimeType { public: void Set(int, int, int) void Increment(); void Display(); intgethours(); intgetminutes(); intgetseconds(); private: int hours; int minutes; int seconds; };

13. Introduction to Object Oriented Programming (OOP) • Constructors • Is a special member function visible to the user that has the same name as the class. • It has no return type nor “void” • It is called when an object is declared and is used to set up the object initially. Only called once during initialization. • You can have more than one constructor but each must have unique parameters.

14. Introduction to Object Oriented Programming (OOP) • Example of a Definition of a class TimeType with contstructor class TimeType { public: TimeType(); TimeType(int h; int m; int s); void Set(int, int, int) void Increment(); void Display(); intgethours(); intgetminutes(); intgetseconds(); private: int hours; int minutes; int seconds; };

15. Introduction to Object Oriented Programming (OOP) // Examples TimeType TodaysTime; TimeType Yesterday(12,24,26); // The first one uses the // constructor with no parameters. // We assume the code will assign // today’s date. // The second uses the constructor with // three parameters to set the actual // hour, minute, and second.