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Class..Object (VB.Net and Delphi Cross Reference Guide)

By Mike Prestwood

VB.Net versus Delphi: A side by side comparison between VB.Net and Delphi.

 
OOP Basics
 

Some languages support object-based concepts such as Paradox, Access, and VB Classic. Other languages have OO extensions and fully support object orientation in a hybrid fashion (such as C++ and Dephi for Win32). Finally, some lanages such as C#, VB.Net, Prism, and Java are entirely written in OO. Meaning, every line of code written must occur within a class).

Class..Object

[Other Languages] 

Languages Focus

In short, a class is a data type, and an object is an instance of a class type. A class has methods (routines), properties (member variables), and a constructor. The current values of the properties is the current state of the object. The UML is one of the diagraming disciplines that allows you to document the various changing states of a series of objects.

VB.Net:   Class..End Class..New

Declare and implement VB.Net classes after the form class or in their own .vb files. Unlike VB Classic, you can have more than one class in a .vb class file (VB classic uses .cls files for each class).

Syntax Example:

Class definition:

Public Class Cyborg
  Inherits Object
 
  Public Sub IntroduceYourself()
  MessageBox.Show("Hi, I do not have a name yet.")
 End Sub
End Class

Some event like a button click:

Dim T1 As New Cyborg
T1.IntroduceYourself()
//No need to clean up with managed classes.
//The garbage collector will take care of it.
Delphi:   class..end..Create

Declare your class in the Interface section. Then implement the class in the Implementation section. To create an object instance, call the class constructor (usually named Create). Since Delphi does not have a garbage collector, you have to also free the object usually with either Free or FreeAndNil.

Syntax Example:
//Interface section:
TCyborg = class(TObject)
public
procedure IntroduceYourself;
end;
 
//Implementation section;
procedure TCyborg.IntroduceYourself;
begin
ShowMessage('Hi, I do not have a name yet.');
end;
 
//Some event like a button click:
var
T1: TCyborg;
begin
T1 := T1.Create;
T1.IntroduceYourself;
  FreeAndNil(T1);      //Be sure to clean up!
end;












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