CODEWITHSUNDEEP
delphirtti
Vic
Vic

Reputation: 11

Delphi - Visual Form Inheritance - Components base classe detection

I'm using VFI (Visual Form Inheritance) and I need to check if a component of an instantiated form belongs to the formclass or to the form superclass.

any ideas ?

  unit1

  TFormStatus = class(TForm)
    cpPanel: TPanel;
    lblStatus: TLabel;
  end;

  unit 2

  TFormCodigo = class(TFormStatus)
    lblCodigo: TLabel;
  end;

  frmCodigo: TFormCodigo:

In any instances of frmCodigo I want to detect that lblCodigo is local to TFormCodigo and cpPanel / lblStatus are inherited components;

  for i:=0 to Self.ComponentCount-1 do begin        
      if "InheritedComponent" (Self.Components[i]) then ...
  end;

Something like this is possible using RTTI for object properties, but I dont know if it is possible for components.

Thanks.

Upvotes: 1

Views: 1133

Answers (3)

Maksee
Maksee

Reputation: 2401

In your TFormCordigo you can override ReadState method that is called every time a resource is read for a particular form. After inherited called ComponentCount contains the number of components created up to the current member of hierarchy, so after all you have list of borders for components that you can save elsewhere.

The code below illustrates this approach

procedure TInhTestForm.Button3Click(Sender: TObject);
var
  i: integer;
begin
  inherited;

  Memo1.Lines.Clear;
  for i:=0 to ComponentCount-1 do
  begin
    Memo1.Lines.Add(format('%s inroduced in %s', [Components[i].Name, ComponentParent(i).ClassName]));
  end;
end;

function TInhTestForm.ComponentParent(Index: integer): TClass;
var
  i, j: integer;
begin
  Result:=Nil;
  for i:=Low(fComponentBorders) to High(fComponentBorders) do
  begin
    if Index <= fComponentBorders[i] - 1 then
    begin
      j:=i;
      Result:=Self.ClassType;
      while j < High(fComponentBorders) do
      begin
        Result:=Result.ClassParent;
        Inc(j);
      end;
      break;
    end;
  end;
end;

procedure TInhTestForm.ReadState(Reader: TReader);
begin
  inherited;
  SetLength(fComponentBorders, Length(fComponentBorders) + 1);
  fComponentBorders[High(fComponentBorders)]:=ComponentCount;
end;

Upvotes: 0

Uli Gerhardt
Uli Gerhardt

Reputation: 13991

Maybe something "stupid" like

function TFormStatus.IsStatusComponent(AComponent: TComponent): Boolean;
begin
  Result := (AComponent = cpPanel) or (AComponent = lblStatus);
end;

already fulfils your needs?

Upvotes: 0

David Heffernan
David Heffernan

Reputation: 612794

If I understand you correctly, you need TRttiMember.Parent. For example see this article by Rob Love. You'll need Delphi 2010 or later I think.

In fact this is just part of an excellent series of articles - these articles will also tell you how to get hold of the fields, properties etc. without having to know their names.

Upvotes: 1

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