Question

In Delphi 2009 I have a Form with a procedure MyProcedure that writes to a label on the Form. The form uses a DataModule with a ClientDataSet. When the AfterScroll event of the ClientDataSet is fired MyProcedure should be executed.
To avoid circular references and more important, as I want the DataModule to be reusable,
the DataModule should not reference to this specific Form.

In short, I hope that I can access the AfterScroll event from my Form. Can I hook up the Afterscroll event on the DataModule from my Form? I thought it should be possible, but I cannot remember how to do it. Thanks in advance.

Answer 1

You need to put an event property in your DataModule:

private
FOnAfterScroll : TNotifyEvent;
public
property OnAfterScroll   : TNotifyEvent read FOnAfterScroll write FOnAfterScroll;

You then call that event in the AfterScroll procedure in the DataModule:

If Assigned(FOnAfterScroll) then FOnAfterScroll(Self);

In Form:
declare event handler

procedure HandleAfterScroll(Sender : TObject);

Then you assign a procedure to DataModule’s OnAfterScroll

 Datamodule1.OnAfterScroll :=
 MyHandleAfterScroll;

Another way would be to send a custom windows message from DataModule and to respond to that message in the Form.