Sam Witse

Dalija,

Thanks, clear explanation.

Any idea how I could define a working 'polymorfic property' ?

12 minutes ago, Uwe Raabe said:

Use a non-static class function

This is exactly what I'm trying to do: 

class function GetChildID: integer; virtual; abstract;

is a virtual class function.

But the Child-version of this class function is not found!

Hi Delphi addicts,

I want to create an "inherited class property".

- I define a class property in Master

- Define a local getter in Master, because a getter must be static

- Define an abstract class procedure, called by the getter

- Implement the class procedure in Child

Writing it in Delphi and compiling it, all goes well.

When executing the code, the getter raises an abstract error when calling the class procedure.

What am I missing?

Is there a way to define inheritable polymorf class properties?

unit Unit1;

interface

type
  TMaster = class
  private
    class function GetMasterId: integer; static; {MUST be a static method for a property getter}
  protected
    class function GetChildID: integer; virtual; abstract;
  public
    class property id: integer read GetMasterId ;
  end;

  TChild = class(TMaster)
  protected
    class function GetChildID: integer; override;
  end;

implementation

{ TMaster }

class function TMaster.GetMasterId: integer;
begin
  result := GetChildID ;   { <= at this point I get an abstract error}
end;

{ TChild }

class function TChild.GetChildID: integer;
begin
  result := 1
end;

end.

procedure TForm2.Button1Click(Sender: TObject);
begin
  Edit1.Text := inttostr(TChild.id)  { <= Calling the Child's property}
end;