1 / 50

CHAPTER ELEVEN

CHAPTER ELEVEN. Multiple Classes and Inheritance. 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. Objectives. Instantiate an object

adie
Télécharger la présentation

CHAPTER ELEVEN

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CHAPTER ELEVEN Multiple Classesand Inheritance

  2. 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 Inheritance

  3. 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 Inheritance

  4. Objectives • Code a base class and a subclass incorporating 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 Inheritance

  5. Preview the Chapter Project Chapter 11: Multiple Classes and Inheritance

  6. User Interface and the TabIndex Property • Select the object that will be selected when program execution begins. In the example, this is the txtStudentIDMaskedTextBox object. Scroll in the Properties window until the TabIndex property is visible and then 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 txtStudentNameTextBox object should be selected. Double-click the right column of the TabIndex property for the txtStudentNameTextBox object, type 2 and then press the ENTER key Chapter 11: Multiple Classes and Inheritance

  7. User Interface and the TabIndex Property Chapter 11: Multiple Classes and Inheritance

  8. User Interface and the TabIndex Property Chapter 11: Multiple Classes and Inheritance

  9. 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. But, 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 Inheritance

  10. Editing Input Data Chapter 11: Multiple Classes and Inheritance

  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 Inheritance

  12. 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 Inheritance

  13. Sample Program Classes • Presentation tier: The presentation tier contains the RegistrationCostForm 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 oncampus 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 Inheritance

  14. Creating a Class • With Visual Studio open and a Window Application project begun, right-click the project name in the Solution Explorer window and then point to Add on the shortcut menu • Click Class on the Add submenu • Type Student as the name of the class and then click the Add button • Using the same techniques, create the OnCampusStudent class and the StudentCostsFile classes Chapter 11: Multiple Classes and Inheritance

  15. Creating a Class Chapter 11: Multiple Classes and Inheritance

  16. Creating a Class Chapter 11: Multiple Classes and Inheritance

  17. Instantiating a Class and Class Communication • Whenever you define a class in your Visual Basic program, you must instantiate, or create, an object based on that class in order for the processing within the object to take place Chapter 11: Multiple Classes and Inheritance

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

  19. 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 Inheritance

  20. Passing Arguments when Instantiating an Object Chapter 11: Multiple Classes and Inheritance

  21. 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 Inheritance

  22. Inheritance • Inheritance allows one class to inherit attributes and procedures from another class Chapter 11: Multiple Classes and Inheritance

  23. Inheritance Chapter 11: Multiple Classes and Inheritance

  24. Inheritance Chapter 11: Multiple Classes and Inheritance

  25. Constructors BASE CLASS CONSTRUCTOR Chapter 11: Multiple Classes and Inheritance

  26. Constructors SUBCLASS CONSTRUCTOR Chapter 11: Multiple Classes and Inheritance

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

  28. 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 Inheritance

  29. Call a Named Procedure in the Base Class Chapter 11: Multiple Classes and Inheritance

  30. Calling an Overridable Procedure in a Base Class Chapter 11: Multiple Classes and Inheritance

  31. Calling an Overridable Procedure in a Subclass Chapter 11: Multiple Classes and Inheritance

  32. Calling a Named Procedure in the Subclass Chapter 11: Multiple Classes and Inheritance

  33. Calling a Base Class Procedure in the Subclass Chapter 11: Multiple Classes and Inheritance

  34. 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, a DVD-ROM or a USB drive Chapter 11: Multiple Classes and Inheritance

  35. Persistence Classes Chapter 11: Multiple Classes and Inheritance

  36. Comma-Delimited Text File Chapter 11: Multiple Classes and Inheritance

  37. Comma-Delimited Text File Chapter 11: Multiple Classes and Inheritance

  38. Program Design Chapter 11: Multiple Classes and Inheritance

  39. Program Design Chapter 11: Multiple Classes and Inheritance

  40. Program Design Chapter 11: Multiple Classes and Inheritance

  41. Event Planning Document Chapter 11: Multiple Classes and Inheritance

  42. Event Planning Document Chapter 11: Multiple Classes and Inheritance

  43. Event Planning Document Chapter 11: Multiple Classes and Inheritance

  44. Event Planning Document Chapter 11: Multiple Classes and Inheritance

  45. Event Planning Document Chapter 11: Multiple Classes and Inheritance

  46. Event Planning Document Chapter 11: Multiple Classes and Inheritance

  47. 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 Inheritance

  48. 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 Inheritance

  49. Summary • Code a base class and a subclass incorporating 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 Inheritance

  50. CHAPTER ELEVEN COMPLETE Multiple Classesand Inheritance

More Related