1. Object-oriented design for multiple classes
Chapter 13
Object-oriented design for multiple classes

2. Objectives
To expand an object-oriented solution to cater for multiple classes
To introduce interface and GUI objects

3. Object-oriented design for multiple classes
13.1
Object-oriented design for multiple classes

4. Object-oriented design for multiple classes
Advantages in using inheritance:
Saves time because the Parent class contains attributes and method that already exist
Reduce errors because the Parent class method have already been tested and used

5. Interface and GUI objects
13.2
Interface and GUI objects

6. Interface and GUI objects
Many popular programming languages provide a graphical user interface (GUI), which enables the programmer to select the elements of the program’s user interface from a pre-existing range of option
Interface design is a subset of a program design, as it concentrates on one aspect of the program’s performance and implementation

7. Interface and GUI objects
The interface are developed from predesigned classes available in the programming language
The use interface option may include windows, buttons, menus, boxes to hold text, drop down list and many more

8. Summary Most object-oriented programs need more than one class.
Classes can be related to each other through association, by aggregation or composition or by inheritance.
Polymorphism allows several operations to have the same name, but they achieve their purposes by different methods.

9. Summary
Using operation overriding, a child class may substitute the parent class version of an operation with its own specific version.
With operation overloading, several operations of the same name may have different numbers of parameters and different algorithms.

10. Summary
Interface design for visual programming languages uses object-oriented design principles.
Interface objects have operations and attributes.
The choice of interface design can reduce the complexity of both an algorithm and the resulting program.