Prototyping for HCI

1. Prototyping for HCI Spring 2004 (Week 8) Jorge A. Toro

2. The Language Custom Classes

3. Custom classes • VB.NET is Object-Oriented • So far, you have handled pre-defined classes (Form, Button, Integer, String, etc…) -but- • You can also create your own classes that can ease the coding and fit the needs of your prototype

4. Custom classes • How do you know when you need a custom class? • You need to do some design decisions on what kind of classes you will need. • There is no golden rule in this, many different classes can be created and used, it all depends how you want to architect your code.

5. Custom classes • When you are writing the code inside a form, you are actually writing the code for the Form’s class…

6. Your form is defined as a class Your form

7. Custom classes • Creating a custom class • Custom classes are created in separate files • Same as different forms are in separate files • To add a custom class file • File -> Add New Item… • Select Class, give a name to it • Done.

8. 1

9. 2 1 Select Class 2Name the Class

10. This code is automatically generated. Here is where you write the code to define the properties and methods of your class. 3 The class file appears in your Solution Explorer window

11. Custom classes • Defining properties for the class • One way: Declare global variables as Public. PublicClass Member Public p_id AsString Public p_lname AsString Public p_fname AsString Public p_address AsString Public p_city AsString Public p_state AsString Public p_zip AsString EndClass Properties

12. Member class

13. Custom classes • Using your custom class • You create instances (objects) of the class • Use the New keyword, the same way you use it to create forms.

14. Form1 class You now can declare Member objects

15. Custom classes • Everything declared with either Dim or Private will not be accessible from outside the class.

16. Member Class p_ssn is not declared Public. It will be accessible only inside this class.

17. Form1 Class x is an instance of Member class p_ssn is not accessible outside the class, it was not declared Public.

18. Custom classes • Defining methods • All the subs and Functions declared Public are considered methods and are accessible outside the class.

19. Member Class ResetNames is a Sub declared Public. It will be accessible outside.

20. Form1 Class ResetNames is accessible.

21. Custom classes • Sometimes, you want your object to start with some preset values in some of its properties. • Constructor • Used to provide values to the properties when an instance is created • You can have different constructors for different situations • A constructor is always declared as Public and it is always named New

22. Constructor1 (default) Constructor2(custom)

23. constructor1 is used here constructor2 is used here

24. The Language Modules

25. Modules • Modules are files where you can write code that does not belong to any particular form. • Global functions • Global Subs • Global variables • Global variables declared in a Module are global to all the project.

27. 1 Select Module 2Name the Module

28. This code is automatically generated. Here is where you write the code. The module file appears in your Solution Explorer window

29. Modules • Sub Main • You can set the Startup Object of your project to a special sub named Main • You create the Sub Main inside a Module file.

30. mainForm is a global variable mainForm is created mainForm is shown

31. Modules • In the previous example, if you set your startup object of your project to be the Sub Main, you have to create the instance of Form1 and show it. • This is useful when you have a prototype with many form files.

32. The Language Class Libraries

33. Class libraries • A separate project for creating classes for use in other applications • This is what you will get from me • A project with some classes inside

34. Class libraries • Using the library in your prototype • (1/2) Add the library into your prototype’s project

36. Select the project name

37. The project appears into the Solution explorer

38. Class libraries • Using the library in your prototype • (2/2) Reference the class library in your project so you can start using the classes • Why do you have to do this? • Because the classes I wrote are inside a separateproject, they are not part of yours.

39. 1 Select your project 2Select “Add Reference”

40. 1 Click over the Projects tab 2 Select the Utils Project 3 Click Select

41. The library will appear here Click Ok

42. The Utils library will appear listed under the References folder in your project

43. Questions?