Object- Oriented Programming in Visual Basic.NET. Heng Sovannarith

Size: px

Start display at page:

Download "Object- Oriented Programming in Visual Basic.NET. Heng Sovannarith"

Posy Elliott
6 years ago
Views:

1 Object- Oriented Programming in Visual Basic.NET Heng Sovannarith

2 IntroducCon OOP is a design philosophy. It stands for Object Oriented Programming. Object- Oriented Programming (OOP) uses a different set of programming languages than old procedural programming languages (C, Pascal, etc.). Everything in OOP is grouped as self sustainable "objects". Hence, you gain re- usability by means of four main object- oriented programming concepts.

3 IntroducCon (cont.) Advantages of OOP Simplicity: solware objects model real world objects, so the complexity is reduced and the program structure is very clear. Modularity: each object forms a separate encty Modifiability: it is easy to make minor changes in the data representacon or the procedures in an OO program. Changes inside a class do not affect any other part of a program.

4 IntroducCon (cont.) Extensibility: adding new features or responding to changing operacng environments can be solved by introducing a few new objects and modifying some exiscng ones; Maintainability: objects can be maintained separately, making locacng and fixing problems easier; Re- usability: objects can be reused in different programs.

5 IntroducCon (cont.) Concepts of OOP: Classes and Object Data AbstracCon and EncapsulaCon Inheritance Polymorphism Interface

6 Class and Object A class is like a template in OOPs, and this template is used to create objects. In general words we can say, that it is a structure of which Objects are instances. Class = Variable + ProperCes + Methods An Object is an instant of a class. For Example: We have class PPIUStudent and Sopha is a student of PPIU so it is an instant of class PPIUStudent.

7 Class and Object (cont.) The basic source code needed to define a class is pre[y simple. Public Class classname statement End Class InstanCaCng an object requires (1) a variable to hold the object and (2) the creacon of the object using the New keyword. These two steps are olen performed in two separate VB statements. Dim myinstance As SimpleClass ' Defines the variable myinstance = New SimpleClass ' Creates the object

8 Class and Object (cont.) These two steps can be combined into a single statement: Dim myinstance As SimpleClass = New SimpleClass A shortcut syntax makes the instancacon even simpler: Dim myinstance As New SimpleClass

9 Class and Object (cont.)

10 Class Members Field Members: This includes member variables and constants. Enumerated data types defined within a class fall into this category. Event Members: Events are procedures that are called automaccally by the Common Language RunCme in response to some accon that occurs, such as an object being created, a bu[on being clicked, a piece of data being changed, or an object going out of scope. Events can also be manually fired through code.

11 Class Members (cont.) Property Members: ProperCes combine aspects of both funccon methods and fields. They are olen used to provide access to a hidden class field through a pair of property procedures, one for updacng the data and one for retrieving the current data value. Type Members: Classes may be nested, with one class contained completely within another.

12 Class Members (cont.) The following Person class sample illustrates all of the various member types except class nescng.

13 Class Member Accessibility Generally, the members of a class consctute that class's public interface. But some members may exist only for the internal use of the class instance itself. Each member of a class includes an access modifier. These special keywords indicate just how visible a parccular member is to code outside of the class.

14 Class Member Accessibility (cont.) There are the five available access modifiers.

15 Constructor

16 Copy Constructor

17 Shared Method

18 EncapsulaCng Data with ProperCes

19 EncapsulaCng Data with ProperCes (cont.)

20 EncapsulaCng Data with ProperCes (cont.)

21 Inheritance

22 Inheritance (cont.)

23 Inheritance (cont.)

24 Polymorphism

25 Polymorphism (cont.)

26 Overriding (Override the exiscng methods of the Base Class)

27 Interface

28 Interface (cont.)

Object Oriented Programming

Object Oriented Programming Haleh Ashki 2015, updated Peter Beerli 2017 Traditionally, a program has been seen as a recipe a set of instructions that you follow from start to finish in order to complete