Delphi fire frame events from datamodule - delphi

Question

I've an application made by a main form, a frame and a datamodule.
When the main form is created I create also the frame wich contains the fields present in a table that are in the datamodule.
So the main form code is this:
unit main;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs,
FraDtl;
type
TfrmMain = class(TForm)
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
FFraDtl: TfraDetail;
public
{ Public declarations }
end;
var
frmMain: TfrmMain;
implementation
{$R *.dfm}
procedure TfrmMain.FormCreate(Sender: TObject);
begin
FFraDtl := TfraDetail.Create(Self);
FFraDtl.Parent := Self;
end;
end.
The code of the frame is this:
unit FraDtl;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs,
database, cxGraphics, cxControls, cxLookAndFeels, cxLookAndFeelPainters,
cxContainer, cxEdit, cxTextEdit, cxDBEdit, Vcl.StdCtrls, dxSkinsCore,
cxNavigator, cxDBNavigator;
type
TfraDetail = class(TFrame)
lblCognome: TLabel;
edtCognome: TcxDBTextEdit;
lblNome: TLabel;
edtNome: TcxDBTextEdit;
cxDBNavigator1: TcxDBNavigator;
private
{ Private declarations }
public
{ Public declarations }
end;
implementation
{$R *.dfm}
end.
And the code of the datamodule is this:
unit database;
interface
uses
System.SysUtils, System.Classes, Data.DB, DBAccess, MSAccess, MemDS,
dxSkinsCore, cxClasses, cxLookAndFeels, dxSkinsForm;
type
TdmData = class(TDataModule)
Connection: TMSConnection;
tblAutori: TMSTable;
dsAutori: TMSDataSource;
fAut_IdAutore: TIntegerField;
fAut_Cognome: TStringField;
fAut_Nome: TStringField;
fAut_Nominativo: TStringField;
SkinController: TdxSkinController;
procedure DataModuleCreate(Sender: TObject);
procedure DataModuleDestroy(Sender: TObject);
procedure dsAutoriStateChange(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
dmData: TdmData;
implementation
{$R *.dfm}
procedure TdmData.DataModuleCreate(Sender: TObject);
begin
tblAutori.Open;
end;
procedure TdmData.DataModuleDestroy(Sender: TObject);
begin
tblAutori.Close;
end;
procedure TdmData.dsAutoriStateChange(Sender: TObject);
begin
// Some stuff
end;
end.
I would like to call a procedure present in the frame in the dsAutoriStateChange event is fired. There is a way to do this?

Answer 1

I would like to call a procedure present in the frame in the dsAutoriStateChange event is fired.
You can do this using code like this:
unit database;
....
implementation
uses FraDtl;
procedure TdmData.dsAutoriStateChange(Sender: TObject);
begin
FraDtl.SomeProcedure;
end;
Or if you want to access the actual instantiated frame you access the main unit.
unit database;
....
implementation
uses main; //circular reference allowed in implementation
procedure TdmData.dsAutoriStateChange(Sender: TObject);
begin
frmMain.FrameDetail.DoSomething(Sender);
end;
In that case you need to add an public property to frmMain exposing the frame.
TfrmMain = class(TForm)
...
public
property FrameDetail: TFraDetail read FFraDtl;
Warning
These kinds of hard coupling between data module and form are considered bad programming practice.
Loose coupling is good
Hard coupling is bad
It would be better to use an event handler for a datasource inside the mainform, or if that's not possible to add additional properties to TdmData that get updated by the main form as needed.
The event handler dsAutoriStateChange can then access these properties instead of having to poke around in the private parts of the frame.