Languages Focus: Base Class

When you create a class, it is either a base class or inherits from another class. Some languages require all classes to inherit from a common base class and some do not.

//Specify both namespace and class:

TCyborg = class(System.TObject)
end;

//Use shortcut alias:

TCyborg = class(TObject)
end;

//None, default is System.TObject

TCyborg = class
end;

Fun With TObject

TObject has some basic functionality available for all Delphi classes. Since TObject is the base class for Delphi, you should become familiar with it's features.

To see TObject in action, alter the click event of a button as follows:

var
  MyObject: TObject;
begin
  MyObject := TObject.Create;       //Create object instance.
  ShowMessage(MyObject.ClassName);  //Return the class name.
  ShowMessage(UnitName);            //UnitName is a class function
                                    //defined in TObject.
  MyObject.Free;                    //Free object instance.
end;

Next, view the source code for TObject to see what routines are implemented. The easiest way to find TObject's declaration is to right click on TObject in your source code and select Find Declaration. Most of these routines are documented in the help so you can place the cursor on any procedure or function name and press F1.

Common Inheritance Choices

The following is a short list of some more common VCL classes you can inherit from.

Step by Step Example

The following is a step-by-step tutorial on creating your first Delphi class and does include an inheritance example. From this simple tutorial, you can then experiment with the various class inheritance features.

• Tutorial: A 10 Minute Your First Delphi Class Quick Start