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Using Classes in ASP |
Written on: Nov, 17th 2001. |
Working with "ASP classes" is really cool and I am sure, if you read this article, you will
also start to write an application in ASP using classes. (Unless you go for ASP .NET)
I am very grateful to Dave Cline, who taught me how to work with Classes in ASP.
In order to know more about this article, I assume the reader has knowledge in Object Oriented Programming Structure (OOPS)
How can we declare classes in ASP?
Classes in ASP can be declared as follows
| <% |
| 1 | Class YourClassName |
| |
| 2 | Private intNum |
| 3 | Private strName |
| 4 | Public strLabel |
| |
| 5 | Private Sub Method1() |
| | ' All statments for Method1 goes here |
| 6 | End Sub |
| |
| 7 | Public Sub Method2() |
| | ' All statments for Method2 goes here |
| 8 | End Sub |
| |
| 9 | Public Function Function1() |
| | ' All statments for Function1 goes here |
| 10 | End Function
| | |
| 11 | End Class |
| %> |
Now. we will go through each line of the above declaration. Line 1 declares a class called
YourClassName Line 2 to Line 4 deals with declaring properties on this class. You can
declare either a property to be Private or Public. As VBScript only deals with Variants, we
cannot specify the dataType of each property.
Their should be a way to communicate with these private and public properties. So, we need to have methods which talks with these properties. To know more about, Object Oriented Programming
in C++, click here
Note: Unless declared Private, all properties and methods are public.
Now, we will see an sample ASP page and a samle class file, which deals with Following is the
| Classes.clas - Extension can by anything. I usually used to use .clas |
| <% |
| Class test |
| |
| private var1 |
| private var2 |
| private var3 |
| |
| Public Sub assign_values(byval arg1, byval arg2, byval arg3) |
| var1 = arg1 |
| var2 = arg2 |
| var3 = arg3 |
| End Sub |
| |
| Public Sub return_values(ByRef arg1, ByRef arg2, ByRef arg3) |
| arg1 = var1 |
| arg2 = var2 |
| arg3 = var3 |
| End Sub |
| |
| Private Sub Class_Initialize() |
| ' Initialization statements goes here (You can call this as a CONSTRUCTOR) |
| End Sub |
| |
| Private Sub Class_Terminate() |
| ' Clearing all the objects goes here (You can call this as a DESTRUCTOR) |
| End Sub |
| |
| End Class |
| %> |
In the above class file, we have three private properties and two public methods which
communicate with the properties. In the following ASP page, we will see, how to invoke
the above class.
| test.asp |
| <!--#include file="Classes.clas"--> |
| <% |
| |
| Dim ObjClass |
| Dim v1, v2, v3 |
| |
| Initialize() |
| |
| Assign 1, 2, 3 |
| |
| GetValues() |
| |
| Response.Write v1 & " " & v2 & " " & v3 |
| |
| Terminate() |
| |
| Sub Initialize () |
| Set ObjClass = New test |
| End Sub |
| |
| Sub Assign(a, b, c) |
| ObjClass.assign_values a, b, c |
| End Sub |
| |
| Sub GetValues() |
| ObjClass.return_values v1, v2, v3 |
| End Sub |
| |
| Sub Terminate () |
| Set ObjClass = Nothing |
| End Sub |
| %> |
In the above ASP page, we are including the Classes.clas file as the first statement. Then in
the procedure called Initialize, we create an instance of class, test. Then, we are passing
assigning values to the three properties using the interface (method) assign_values. After that,
using the interface GetValues, we are retrieving the values of those three properties. The above is just an example that depicts the
usage of classes in ASP. Although, the example just assigns some values to the properties and retrieves those values with the
help of another method. We can do a lots of things with classes. The following example
Now, we are going to see a real time example for the use of classes. We are going to create a class called Student, which can
hold details of students. We have four properties and two methods. First lets look into the Class definition
| Student.clas |
| <% |
| Class Student |
| |
| private S_Name |
| private S_DOB |
| private S_Sex |
| private S_Class |
| |
| Sub loadFromHTMLForm() |
| S_Name = Cstr(Trim(Request.Form("Name"))) |
| S_Dob = CDate(Trim(Request.Form("Dob"))) |
| S_Sex = Cstr(Trim(Request.Form("sex"))) |
| S_Class = Cstr(Trim(Request.Form("Class"))) |
| End Sub |
| |
| Function Save() |
| Dim StrQuery |
| ' Your connection statments goes here |
| StrQuery = "Insert Into Student (Roll, Name, DOB, Sex, Class) Values " |
| StrQuery = StrQuery + "('" & S_Name & "','" & S_DOB & "','" & S_Sex & "','" & S_Class & "')" |
| connection.Execute strquery |
| ' other statements goes here |
| Save = "Any Return Value" |
| End Function |
| |
| End Class |
| %> |
Now, we will see the ASP page, which uses this class.
| Student.asp |
| <!--#include file="Student.clas"--> |
| <% |
| Dim ObjStudent |
| |
| Initialize() |
| |
| ObjStudent.loadFromHTMLForm() |
| |
| Response.Write ObjStudent.Save() |
| |
| Terminate() |
| |
| Sub Initialize () |
| Set ObjStudent = New Student |
| End Sub |
| |
| Sub Terminate () |
| Set ObjStudent = Nothing |
| End Sub |
| %> |
Summary
This is just a simple example. You can also use the dictionary object as one of the property in the Class Definition and you can
and fill up the dictionary objects and you can use them, while displaying a recordset. As we are using OOP concept, all the
advantages of OOP applies in this example too. Happy Programming.
External Links
http://www.gnacademy.org/text/cc/Tutorial/tutorial.html
http://java.sun.com/docs/books/tutorial/java/concepts/
Send your comments to das@aspalliance.com
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