Silly question...

Say your MDIChild is named Child2...

  Child2.RichEdit1

should do it...

MainForm.ActiveMDIChild.richedit1

Suppose it is NOT the Active child???

TFormClassWithRichedit(ActiveMDIChild).richedit1

or

TFormClassWithRichedit(MDIChildren[index]).richedit1

whereas
TFormClassWithRichedit is the Class declaration od your MDIChild

meikl ;-)

typo
od -> of

hmmm i am still getting error: "Undeclared identifier : RichEdit1".
I don't get it...

You must include the unit that contains the MDIChild in your implementation uses clause.
From the Main Menu, select File->Use Unit and select the unit that contains the MDIChild
that contains the RichEdit.

Eddie's will work.
sgc_romana's wont.
kretzschmar's will, too, so long as you use the right class name(!)

Sounds like you're using Eddie's method.

a sample

--- main-unit

unit mdi_re_main_u;

interface

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

type
  TForm1 = class(TForm)
    Panel1: TPanel;
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses mdi_re_child_u;  //child-unit used

procedure TForm1.Button1Click(Sender: TObject);
begin
  with TForm2.Create(self) do show;
end;

procedure TForm1.Button2Click(Sender: TObject);
var i, childs, lines : integer;
begin
  childs := MDIChildCount;
  lines := 0;
  for i := 0 to MDIChildCount -1 do
    if (MDIChildren[i] is TForm2) then
      lines := lines + TForm2(MDIChildren[i]).RichEdit1.Lines.Count;

  Showmessage('There are '+inttostr(childs)+' Childs'+#10+
              'Which are Containing in Sum '+inttostr(lines)+' Lines Text');

end;

end.

---- Child-Unit
unit mdi_re_child_u;

interface

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

type
  TForm2 = class(TForm)
    RichEdit1: TRichEdit;
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

procedure TForm2.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  action := caFree;
end;

end.

---------

meikl ;-)

Thanks but here is what i need. When i press a button on the toolbar, i want "You pressed button1..." or any other text to be displayed in the RichEdit1 of the Active MDIChild (something like ActiveMDIChild.RichEdit1.Add('sdkfsdh')- only it doesn't work).  Thanks very much for even reading up to here and i know i am very boring but i can't get this to work.

You can't do it directly that way. 'ActuveMDIChid' is a TForm. A TForm doesn't have a RichEdit1 component. So you can't do it generically.

Either:

Derive all your MDI child forms from some base class which _does_ have a RichEdit1 component.

Then you could do

TBaseMDIForm( ActiveMDIChlid ).RichEdit1.Add('asldkajslkd');

or, check to see which class the Active chlid is..

if ActiveMDIChild is TFirstChlidForm then
  TFirstChildForm(ActiveMDIChild).RicheEdit1.Add('asdasd');
else if ActiveMDIChlid is TSecondChildForm then
  TSecondChlidForm(...)...
else ...

etc.

depending on how many chlid form class types you've got.

NB "You can't do it directly that way" applies to T-104's last comment, not meikl's !

Thanks alot guys you helped me alot!! it works now!!!