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► KB ► Website Scri... ► ASP Classic ► OOP

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From the January 2016 Issue of Prestwood eMag

ASP Classic OOP:

ASP Classic Constructors (Class_Initialize)

By Mike Prestwood

Posted 10 years ago on 1/18/2009

ASP Classic Code Snippet:

To/From Code Guide: ASP Classic Construc... vs. Other Languages

A flashcard from our ASP Classic Flashcards Library

A code snippet from our ASP Classic Code Snippets Page

Tags: ASP Classic , Constructor , Constructors

KB101823

General Info: Class Constructor

Constructors are called when you instantiate an object from a class. This is where you can initialize variables and put code you wish executed each time the class is created. When you initially set the member fields and properties of an object, you are initializing the state of the object. The state of an object is the values of all it's member fields and properties at a given time.

Languages Focus: Constructor

What is the syntax? Can you overload constructors? Is a special method name reserved for constructors?

ASP Classic Constructors

When an object instance is created from a class, ASP calls a special parameter-less sub named Class_Initialize. Since you cannot specify parameters for this sub, you also cannot overload it.

When a class is destroyed, ASP calls a special sub called Class_Terminate.

Syntax Example:

Class Cyborg
  Public CyborgName
 
  Public Sub Class_Initialize
   Response.Write "<br>Class created"
   CyborgName = "Cameron"
  End Sub

End Class

Working Example

The following working example contains both a constructor and destructor, ASP's Class_Initialize and Class_Terminate subs. In this example, we are implicitly destroying the object (letting IIS destroy the object when the variable goes out of scope).

You can explicitly destroy an object by using Set MyRobot = Nothing. In ASP Classic, it is recommended that you explicitly destroy all objects.

<%@LANGUAGE=VBScript%>
<%Option Explicit%>
<html>
<body>

<%
Dim MyRobot

Set MyRobot = new Cyborg
Response.Write "<br>My robot's name is " & MyRobot.CyborgName & "."

//Object destroyed implicitly here

//and Class_Terminate is called.
%>

</body>
</html>

<%
Class Cyborg
 Public CyborgName
 
 Public Sub Class_Initialize
  Response.Write "<br>Class created"
  CyborgName = "Cameron"
 End Sub

 Public Sub Class_Terminate
  Response.Write "<br>Class destroyed"
 End Sub 
End Class
%>

More Info

Definition:

Class Constructor

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Code Contributed By Mike Prestwood:

Mike Prestwood is a drummer, an author, and creator of the PrestwoodBoards online community. He is the President & CEO of Prestwood IT Solutions. Prestwood IT provides Coding, Website, and Computer Tech services. Mike has authored 6 computer books and over 1,200 articles. As a drummer, he maintains play-drums.com and has authored 3 drum books. If you have a project you wish to discuss with Mike, you can send him a private message through his PrestwoodBoards home page or call him 9AM to 4PM PST at 916-726-5675 x205.

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Linked Certification Question(s)

The following are practice certification questions with answers highlighted. These questions were prepared by Mike Prestwood and are intended to stress an important aspect of this KB post. All our practice questions are intended to prepare you generally for passing any certification test as well as prepare you for professional work.

Advanced

1 Advanced Level Question

Question #1: Multiple Choice

In ASP Classic object oriented programming, when an object instance is created from a class, ASP calls a special parameter-less sub named what?

Answer:

Class_New

New

Initialize

Class_Initialize

Class_Create

KB Article #101823 Counter

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Since 1/18/2009