Peter

>Just curious, is that activated by a timer, a EDBDBDataSet.AfterPost or does it respond to some form of database Notification?

None of the above

If you look at te function header you'll see (var Message: TMessage); which indicates that it responds to a Windows message. In this case its generated by a menu button click which calls

procedure TMainForm.SendRefreshMessage(Tag: integer);
begin
if IsCreated[tagProject] and ((Tag < 0) or (Tag = tagProject)) then
 PostMessage(frmHndl[tagProject], DoRefreshRequest, 0, 0);
if IsCreated[tagCompanies] and ((Tag < 0) or (Tag = tagCompanies)) then
 PostMessage(frmHndl[tagCompanies], DoRefreshRequest, 0, 0);
if IsCreated[tagContacts] and ((Tag < 0) or (Tag = tagContacts)) then
 PostMessage(frmHndl[tagContacts], DoRefreshRequest, 0, 0);
if IsCreated[tagIntroductions] and ((Tag < 0) or (Tag = tagIntroductions)) then
 PostMessage(frmHndl[tagIntroductions], DoRefreshRequest, 0, 0);
if IsCreated[tagOrderBook] and ((Tag < 0) or (Tag = tagOrderBook)) then
 PostMessage(frmHndl[tagOrderBook], DoRefreshRequest, 0, 0);
if IsCreated[tagEMails] and ((Tag < 0) or (Tag = tagEMails)) then
 PostMessage(frmHndl[tagEMails], DoRefreshRequest, 0, 0);
if IsCreated[tagAlarms] and ((Tag < 0) or (Tag = tagAlarms)) then
 PostMessage(frmHndl[tagAlarms], DoRefreshRequest, 0, 0);
if IsCreated[tagLTC] and ((Tag < 0) or (Tag = tagLTC)) then
 PostMessage(frmHndl[tagLTC], DoRefreshRequest, 0, 0);
if IsCreated[tagCallbacks] and ((Tag < 0) or (Tag = tagCallbacks)) then
 PostMessage(frmHndl[tagCallbacks], DoRefreshRequest, 0, 0);
end;

In this application I have multiple forms hosted on a pagecontrol (much better than MDI in my opinion). Whlst I have a datamodule with the engine, session and database I decided to have separate table instances on each form so its possible for them to get out of synch. Click on the menu button and it send a refresh message to each of the principal forms that is open.. Each form has a function that responds to the message in its own way.

You've seen the one for contacts here's the one for the email form

procedure TProjectForm.ExecuteRefreshRequest(var Message: TMessage);
begin
case Self.Tag of
 tagProject: if iProject <> 0 then GrabProject(iProject, iProjectName);
 tagCallbacks: GrabNonProject(tagMode, 'Contact');
 tagAlarms: PostMessage(Self.Handle, ConfigureProjectPage, 0, 0);
else begin
  if tagMode = tmHeadhunt then
   GrabNonProject(tagMode, Project.IndexName)
  else
   GrabProject(iProject, iProjectName);
 end;
end;
SyncTables(Self);
end;


As you see - same name (just because its easier to remember), different actions.

Roy Lambert

Roy Lambert wrote:

<<None of the above >

Another great idea. I hadn't considered using Messages, but I will now.

Thanks Roy

Peter

Peter


If you start slinging messages around beware! It is possible for a window's handle to be recreated (including a form's). Its not a massively common event but if you look through the VCL code you'll see lots of RecreateWnd calls.

What I've do is declare a common variable (ie declared in a shared and used everywhere unit) and then in the main forms OnCreate

MainHWND := Classes.AllocateHWND(MainHWNDHandler);

This

 procedure MainHWNDHandler(var msg: TMessage);

which is my own message handler goes in the main form's type declaration

procedure TMainForm.MainHWNDHandler(var msg: TMessage);
var
pca: TPageCloseAction;
begin
if MonitorIsOn and (not RunningIsolated) then begin
 case msg.Msg of
  CloseMainProject: begin
    FormControllerClosePage(Self, tagProject, pca);
    FormController.ActivePageIndex := 0;
   end;
{$IFNDEF NOALARMCHECKS}
  AlarmPopupMessage: DisplayPopupAlarm(msg);
{$ENDIF}
  ProgressReport: FilterResult(msg);
  jmpRequired: ProcessJumpInstruction(msg);
  StatusMessage: ChangeStatusMessage(msg);
  PinToJump: AddToJumpButton(msg);
....
....
  PingingDone: if not AppClosing then ToolsMnu.MnuImage[mnuPingTest] := -1;
  //roy alter to refreshing email display   EMailsSkipped: EmailsHaveBeenSkipped(msg);
 else
  msg.Result := DefWindowProc(Self.Handle, msg.Msg, msg.wParam, msg.lParam);
 end;
end else msg.Result := DefWindowProc(Self.Handle, msg.Msg, msg.wParam, msg.lParam);
end;


Finally, in the FormClose event I have a call to    RemoveMainHWND;

procedure TMainForm.RemoveMainHWND;
var
Instance: Pointer;
begin
Instance := Pointer(GetWindowLong(MainHWND, GWL_WNDPROC));
if Instance <> @DefWindowProc then
 // make sure we restore the old, original windows procedure before leaving
 SetWindowLong(MainHWND, GWL_WNDPROC, Longint(@DefWindowProc));
FreeObjectInstance(Instance);
DestroyWindow(MainHWND);
end;


Roy Lambert

Peter

You have a number of options. One which I think should work, and would be fairly easy given the way your app is written, would be to iterate the DM changing property values based on Class-Type.

In the code below, I am assuming your DM is called "Datamodule1" and the Database name is passed around as: MyLocalDatabaseNameVariable. Obviously you'll have to reset all these to the correct names in your app.

(Please note I haven't tested this code at all, but I hope it will provide you with a useful pointer)

<Add this code to some procedure in your application, such as "BeforeConnect" of Database or Session>
var
 i : integer;
begin
 for i:= 0 to DataModule1.ComponentsCount - 1 do
   begin
      if Datamodule1.Components[i] is TEDBSession then
         (Datamodule1.Components[i] as TEDBSession).DatabaseName:= MyLocalDatabaseNameVariable
//          ... add lines to set any other properties for the EDBSession here ...
      if Datamodule1.Components[i] is TEDBDatabase then
         (Datamodule1.Components[i] as TEDBDatabase).DatabaseName:= MyLocalDatabaseNameVariable


   end;
end;

Hope this is useful.