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Class..Object (JavaScript and Delphi Prism Cross Reference Guide)

By Mike Prestwood

JavaScript versus Delphi Prism: A side by side comparison between JavaScript and Delphi Prism.

 
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.

JavaScript:   Limited, class..new

Creating classes in JavaScript is not really OOP, but rather a super type. That is, a type that has some class-like features but is missing the necessary OOP requirements.

There is nothing in Javascript to stop you from accessing the functions within your class outside of the class so this is not fully OOP but is usable.

Syntax Example:
//Class definition.
function Person() {
this.name = 'unknown';
this.age = 0;
}
 
//Use object created from class.
var Lisa = new Person();
Lisa.name='Lisa';
Lisa.age=28;
Delphi Prism:   class..end..new

Declare your class in the Interface section. Then implement the class in the Implementation section. To create an object instance, use the New keyword. Optionally, you can use Create for backword compatibility with Delphi if you turn it on in the compatibility options. Since Prism does have a garbage collector, you do not have to free the object. If you need to free either unmanaged resources or resources where "timing" is important, implement IDisposable and take control of freeing the object yourself using Dispose.

Syntax Example:

In the interface section:

Cyborg = class(System.Object)
public method IntroduceYourself();
end;

In the Implementation section:

method Cyborg.IntroduceYourself();
begin
MessageBox.Show("Hi, I do not have a name yet.");
end;

On some event like a button click:

var T1: Cyborg;
begin
T1 := New Cyborg;
T1.IntroduceYourself;
  //No need to clean up with managed classes.
  //The garbage collector will take care of it.
end;












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