Base Class Inheritence Question

[PaulField1]

I have three classes A, B, C each inherriting from one another B=Class(A), C=Class(B). I have a virtual operation AddXYToSeries in each class. Class B adds some additional functionality then calls inherited AddXYToSeries. Class C adds some further functionality but needs to call Class A AddXYToSeries operation not the inherited Class B AddXYToSeries. Does anyone know the correct syntax to do this? In C++ (ahh!) you just call A::AddXYToSeries from within C::AddXYToSeries member function to get the appropriate one.

I've tried casting Self back to the base clase
A(Self).AddXYToSeries and (Self as A).AddXYToSeries but it just calls itself not the class A operation and I get a stack overflow.
I've also tried
inherited A.AddXYToSeries;
but the compiler did not like it.

 

[JES1904]

I think this might be the way to access the inherited method:
inherited addxytoseries

 

[JES1904]

Sorry about previous post, I misread your last lines.
I have not tried reaching back through several generations and am not sure how to skip the B level.

 

[roo0047]

First, have a look here: thread102-1431491

I got what you described working with:

unit testvirtual;

interface

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

type
  TForm1 = class(TForm)
    RunABtn: TButton;
    RunBBtn: TButton;
    RunCBtn: TButton;
    procedure RunABtnClick(Sender: TObject);
    procedure RunBBtnClick(Sender: TObject);
    procedure RunCBtnClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

  TA = class
    procedure AddXYToSeries; virtual; //abstract;
  private
    { Private declarations }
  public
    { Public declarations }
  end;

  TB = class(TA)
    procedure AddXYToSeries; override;
  private
    { Private declarations }
  public
    { Public declarations }
  end;

  TC = class(TA)
    procedure AddXYToSeries; override;
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TA.AddXYToSeries;
begin
  showMessage('Run from A')
end;

procedure TB.AddXYToSeries;
//Class B adds some additional functionality
//then calls inherited AddXYToSeries.
begin
  showMessage('Run from B');
  Inherited;
end;

procedure TC.AddXYToSeries;
//Class C adds some further functionality but needs
//to call Class A AddXYToSeries operation ...
//... NOT the inherited Class B AddXYToSeries.
begin
  showMessage('Run from C');
  Inherited;
end;

procedure TForm1.RunABtnClick(Sender: TObject);
var a: ta;
begin
  a:= ta.Create;
  a.AddXYToSeries;
  a.Free
end;

procedure TForm1.RunBBtnClick(Sender: TObject);
var b: tb;
begin
  b:= tb.Create;
  b.AddXYToSeries;
  b.Free
end;

procedure TForm1.RunCBtnClick(Sender: TObject);
var c: tc;
begin
  c:= tc.Create;
  c.AddXYToSeries;
  c.Free
end;

end.

Note the only variation in your objective:
B=Class(A), C=Class(B)
is:
B=Class(A), C=Class(A)

But it does what you asked for.
If C MUST inherit from B, then there's more work to do. Hopefully it's start.

Roo
Delphi Rules!