[UOPL-Architect] Maybe Helper Classes would help.

[Richard B W. <rb...@us...>]

There is a new language feature in Delphi2005 for Win32 that might be
useful for some of the things we would like to do with UOPL: Helper
Classes.  One thing you can do with them is replace an existing procedure
of a class with a new procedure from a different class that is not the
descendent of the first class.

Although helper classes are only documented for Delphi for .NET, they work
in Delphi for Win32 too.

See http://www.aspfree.com/c/a/.NET/The-Delphi-Language-Part-2/9/ for more
information.

Here is an example.

unit Unit5;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls,
Forms,
  Dialogs, StdCtrls;

type
  TFoo = class
  strict protected
    procedure AProc; virtual;
  end;

  TFooDescendent = class(TFoo)
    procedure AProc; override;
  end;

  TFooHelper = class helper for TFoo
    procedure AProc;
  end;

type
  TForm5 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form5: TForm5;

implementation

{$R *.dfm}

{ TFoo }

procedure TFoo.AProc;
begin
  ShowMessage('TFoo');
end;

{ TFooHelper }

procedure TFooHelper.AProc;
begin
  ShowMessage('TFooHelper');
end;

{ TFooDescendent }

procedure TFooDescendent.AProc;
begin
  inherited;
  ShowMessage('TFooDescendent');
end;


procedure TForm5.Button1Click(Sender: TObject);
var
  Foo: TFoo;
  FooDescendent: TFooDescendent;
begin
  FooDescendent := TFooDescendent.Create;
  try
    // TFooHelper.AProc and TFooDescendent.AProc get called here
    // but not TFoo.AProc!
    FooDescendent.AProc;
    Foo := FooDescendent;
    // Only  TFooHelper.AProc gets called here. :-(
    Foo.AProc;
  finally
    FooDescendent.Free;
  end;
end;

end.

Richard B. Winston
rb...@us...
http://water.usgs.gov/nrp/gwsoftware/
703-648-5988
on Fridays: 301 474-2762