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Microsoft Visual Basic 2012 CHAPTER ELEVEN Multiple Classes and Inheritance.

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Presentation on theme: "Microsoft Visual Basic 2012 CHAPTER ELEVEN Multiple Classes and Inheritance."— Presentation transcript:

1 Microsoft Visual Basic 2012 CHAPTER ELEVEN Multiple Classes and Inheritance

2 11 Objectives ►Use the TabIndex Property ►Edit input, including MaskedTextBox,TextBox, and ComboBox objects ►Describe the three-tier program structure ►Understand a class ►Create a class Chapter 11: Multiple Classes and Inheritance2

3 11 Objectives ►Instantiate an object ►Pass arguments when instantiating an object ►Write a class constructor ►Call a procedure in a separate class Chapter 11: Multiple Classes and Inheritance3

4 11 Objectives ►Code a base class and a subclass to incorporate inheritance ►Call procedures found in a base class and a subclass ►Write overridable and overrides procedures ►Create and write a comma-delimited text file Chapter 11: Multiple Classes and Inheritance4

5 11 Use the TabIndex Property in the User Interface ►Select the object that will be selected when program execution begins. In the example, this is the txtStudentID MaskedTextBox object. Scroll in the Properties window until the TabIndex property is visible and then double-tap or double-click in the right column of the TabIndex property ►Type 1 and then press the ENTER key ►Select the object which should be selected when the user presses the TAB key. In the sample program, the txtStudentName TextBox object should be selected. Double-tap or double-click the right column of the TabIndex property for the txtStudentName TextBox object, type 2 and then press the ENTER key Chapter 11: Multiple Classes and Inheritance5

6 11 Use the TabIndex Property in the User Interface Chapter 11: Multiple Classes and Inheritance6

7 11 Editing Input Data ►Student ID: The student ID object is a masked text box and the mask is for the Social Security number, so the mask ensures that the user can enter only numbers. However, the Social Security mask does not ensure the user enters all nine numbers. Therefore, a check must be included in the program to require the user to enter all 9 numeric digits. ►Student Name: The program must ensure the user enters characters in this TextBox object. In addition, spaces cannot be entered instead of actual alphabetic characters. ►Number of Units: The user must enter a numeric value from 1 through 24 for the number of units the student is taking. ►Major: The user must select a major from the list in the Major ComboBox object. Chapter 11: Multiple Classes and Inheritance7

8 11 Editing Input Data Chapter 11: Multiple Classes and Inheritance8

9 11 Program Structure Using Classes ►The concept of separating processing and hiding data within specific classes is called encapsulation ►When developing programs with multiple classes, a starting point for determining what classes should appear in a program is the three-tier program structure Chapter 11: Multiple Classes and Inheritance9

10 11 Program Structure Using Classes ►The presentation tier contains the classes that display information for the user and accept user input ►The business tier contains the logic and calculations that must occur in order to fulfill the requirements of the program ►The persistence tier, sometimes called the data access tier, contains the code required to read and write data from permanent storage Chapter 11: Multiple Classes and Inheritance10

11 11 Sample Program Classes ►Presentation tier: The presentation tier contains the frmCollege class. This class displays the user interface in a Windows Form object and also edits the user input data to ensure its validity ►Business tier: The business tier contains two classes: the Student class and the OnCampusStudent class. The Student class contains data for each registered student and calculates the registration costs for some students. The OnCampusStudent class is used for registered students who live in on-campus residence halls ►Persistence tier: The persistence tier consists of one class, StudentCostsFile, which creates and writes the Student Costs File Chapter 11: Multiple Classes and Inheritance11

12 Creating a Class ►With Visual Studio open and a Window Application project started, press and hold or right-click the project name in the Solution Explorer window and then point to Add on the shortcut menu ►Tap or click Class on the Add submenu ►In the Name text box, type Student as the name of the class and then tap or click the Add button ►Using the same techniques, create the OnCampusStudent class and the StudentCostsFile classes Chapter 11: Multiple Classes and Inheritance12

13 11 Creating a Class Chapter 11: Multiple Classes and Inheritance13

14 11 Instantiating a Class and Class Communication ►A class acts as a template for an object Chapter 11: Multiple Classes and Inheritance14

15 11 Constructors in New Instantiated Classes ►When a class is instantiated into an object using the New keyword, a special procedure called a constructor is executed in the class ►The constructor prepares the object for use in the program Chapter 11: Multiple Classes and Inheritance15

16 11 Passing Arguments when Instantiating an Object ►Often when instantiating an object, data must be passed to the object ►In the Student class, the New statement must be written with corresponding arguments; that is, the “signature” of the instantiating statement must be the same as the constructor heading in the class Chapter 11: Multiple Classes and Inheritance16

17 11 Passing Arguments when Instantiating an Object Chapter 11: Multiple Classes and Inheritance17

18 11 Calling a Procedure in a Separate Class ►Most of the time, separate classes in a program contain procedures that must be executed Chapter 11: Multiple Classes and Inheritance18

19 11 Inheritance ►Inheritance allows one class to inherit attributes and procedures from another class Chapter 11: Multiple Classes and Inheritance19

20 11 Inheritance Chapter 11: Multiple Classes and Inheritance20

21 11 Inheritance Chapter 11: Multiple Classes and Inheritance21

22 11 Constructors Chapter 11: Multiple Classes and Inheritance22

23 11 Constructors Chapter 11: Multiple Classes and Inheritance23

24 11 Inheritance and Procedures ►When using inheritance, the subclass can use the procedures within the base class as well as its variables ►Between the base class and the subclass, five different techniques can be used for referencing and calling a procedure from an outside class such as a Form class ►After the base class and the subclass have been instantiated, the following techniques are available: Chapter 11: Multiple Classes and Inheritance24

25 11 Inheritance and Procedures ►Base Class Call a named procedure in the base class Call an Overridable procedure in the base class ►Subclass Call an Overridable Procedure in the subclass Call a named procedure in the subclass Call a base class procedure in the subclass Chapter 11: Multiple Classes and Inheritance25

26 11 Call a Named Procedure in the Base Class Chapter 11: Multiple Classes and Inheritance26

27 11 Calling an Overridable Procedure in a Base Class Chapter 11: Multiple Classes and Inheritance27

28 11 Calling an Overridable Procedure in a Subclass Chapter 11: Multiple Classes and Inheritance28

29 11 Calling a Named Procedure in the Subclass Chapter 11: Multiple Classes and Inheritance29

30 11 Calling a Base Class Procedure in the Subclass Chapter 11: Multiple Classes and Inheritance30

31 11 Persistence Classes ►The persistence tier in an application, sometimes called the data access tier, contains classes that are involved in saving and retrieving data that is stored on a permanent storage medium such as a hard disk or a USB drive Chapter 11: Multiple Classes and Inheritance31

32 11 Persistence Classes Chapter 11: Multiple Classes and Inheritance32

33 11 Comma-Delimited Text File Chapter 11: Multiple Classes and Inheritance33

34 11 Comma-Delimited Text File Chapter 11: Multiple Classes and Inheritance34

35 11 Program Design Chapter 11: Multiple Classes and Inheritance35

36 11 Program Design Chapter 11: Multiple Classes and Inheritance36

37 11 Program Design Chapter 11: Multiple Classes and Inheritance37

38 11 Event Planning Document Chapter 11: Multiple Classes and Inheritance38

39 11 Event Planning Document Chapter 11: Multiple Classes and Inheritance39

40 11 Event Planning Document Chapter 11: Multiple Classes and Inheritance40

41 11 Event Planning Document Chapter 11: Multiple Classes and Inheritance41

42 11 Event Planning Document Chapter 11: Multiple Classes and Inheritance42

43 11 Event Planning Document Chapter 11: Multiple Classes and Inheritance43

44 11 Summary ►Use the TabIndex Property ►Edit input, including MaskedTextBox,TextBox, and ComboBox objects ►Describe the three-tier program structure ►Understand a class ►Create a class Chapter 11: Multiple Classes and Inheritance44

45 11 Summary ►Instantiate an object ►Pass arguments when instantiating an object ►Write a class constructor ►Call a procedure in a separate class Chapter 11: Multiple Classes and Inheritance45

46 11 Summary ►Code a base class and a subclass to incorporate inheritance ►Call procedures found in a base class and a subclass ►Write overridable and overrides procedures ►Create and write a comma-delimited text file Chapter 11: Multiple Classes and Inheritance46

47 Microsoft Visual Basic 2012 CHAPTER ELEVEN COMPLETE Multiple Classes and Inheritance


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