1. Working With Objects Tonga Institute of Higher Education

2. Introduction Visual Basic.NET is an object-oriented language The building block of an object-oriented language is an object. Object - A self-contained entity that contains data and procedures to manipulate the data. An object is like a tool that we can use to do things. You can find a list of pre-built objects in the MSDN Documentation. (www.msdn.com)

3. Advantages of Object Oriented Programming Code is easier to maintain  Code is more readable  Encapsulation Show what the object can do  This is normally what we want to know Hide how the object does it  This can be very complicated  We often don’t care how it is done Code is easier to reuse  A piece of code, once written, should not be thrown away. It is best to reuse the code in other programs.  Example: Millions of people use MessageBox.Show(...). But it was only written once. Code development is more efficient  You don’t code the same thing over and over again

4. Objects Objects are like variables with extra functionality.  Look at MSDN documentation to find functionality. Examples:  String  String.Replace(…)  String.PadLeft(…)  TextBox  TextBox.Text(…)  TextBox.MaxLength(…)

5. Classes vs. Objects Object - A self-contained entity that contains data and procedures to manipulate the data. Class - The blue print or design for creating an object. Instantiate – The act of creating an object from a class Instance – An instantiated class/object

6. Using Object Variables 2 Steps to using variables 1. Declare the variable 2. Instantiate the variable / Initialize the variable

7. Declaring Object Variables – 1 Declare the variable – Tell the computer to reserve a space in memory for the variable. You need to tell the computer 2 things: 1. Name of the variable 2. Type of the variable (What kind of variable you have) String StringBuilder TextBox Type Name

8. Declaring Object Variables – 2 Use a name that is easy to remember.  Do not use x, y, z Begin each separate word in a name with a capital letter Examples  FirstName  CustomerID This works exactly the same for primitive variables!

9. Instantiating Object Variables / Initializing Object Variables Initialize the variable – Assign an initial value to a variable Instantiate – The act of creating an object from a class Use the new keyword New KeywordType of Object Sometimes extra data is required

10. Declaring and Initializing Object Variables in 1 line You can declare and initialize a variable in 1 line.

11. Demonstration Declaring, Instantiating and Initializing Objects

12. Methods Methods - Pieces of code that perform a single function  Use dot notation to access it Example:. ( )  You can find a list of methods in the MSDN Documentation.  You can also find a list of methods using the IntelliSense capability. Calling a Method – The act of using a method

13. Method Inputs - 1 Some methods take inputs  Parameter/Arguments – A piece of information that provides additional information to the method as to how it should behave.  Parameters should be in the parenthesis next to the method name  The order they are passed is important  Values are separated by commas  If you are not passing any parameters, you may or may not use (). It is up to you. Example: String.Trim Example: String.Trim() Method InputOutput

14. Method Inputs - 2 Some methods take inputs  You can find a list of parameters in the MSDN documentation.  You can find a list of parameters using the IntelliSense capability. Method InputOutput Click on link to get more information Method Name Parameters

15. Method Outputs Some methods return outputs  When something is returned, it may or may not be used. The programmer chooses what to do with the data returned.  Only one thing may be returned.  If something is coming back, we can see “As ” at the end of the method in IntellliSense  If nothing is coming back, you will not see “As ” at the end of a method in IntellliSense  Use popup windows while coding to see what is being returned Method InputOutput Information

16. Functions vs. Subroutines Subroutine – A method that does not return anything Function – A method that returns something

17. Demonstration Methods

18. Constructor Constructor – A method that is automatically executed when an object is created.  This allows you to set initial values for the object.  Many objects have multiple constructors. (They are overloaded) You can find a list of constructors in the MSDN Documentation. You can also find a list of constructors using the IntelliSense capability. Dim x as StringBuilder = new StringBuilder Dim y as StringBuilder = new StringBuilder(“hello”) Dim z as StringBuilder = new StringBuilder(6) You don’t need parenthesis if you are not passing parameters

19. Demonstration Constructors

20. Attributes / Fields / Properties Attributes / Fields / Property – A variable that a class allows others to see  Use dot notation to access it Example:. You can find a list of attributes / fields / properties in the MSDN Documentation. You can also find a list of attributes / fields / properties using the IntelliSense capability.

21. Demonstration Attributes / Fields

22. Method Overloading If two methods do the same thing, they should have the same name Overloading - Having multiple methods with the same name but different parameters The correct method to use is determined by matching up the number and type of arguments. Therefore, you can’t have 2 methods with the same name and same number & type of arguments. Without overloading, we would have to remember more function names. That would make code more complicated.

23. Demonstration Overloaded methods

24. Members Member – An attribute/field or method. Sometimes used to refer to the both as a whole.