How to break up TPageControl tabs into seperate files in Delphi?

I have a VCL form with a five tab TPageControl on it. Each TTabSheet's content is fairly unrelated and has a lot of individual controls and processing logic...so I want to break it up so it's easier to deal with the code for "just that tab". Having a line like

//-------------------------- begin rules tab methods -------------------

just isn't cutting it anymore. Really, I think I'd like each tab in a separate file somehow.

Currently I'm contemplating creating a VCL Frame for each TTabPage. If I did so I'd either need to load all the frames into the TPageControl in the constructor, or when the tab is shown.

Is this a good approach? Would it be better to make a whole TForm for each tab? Should I continue to wrap the tabs in a TPageControl, or should that be changed to a TTabControl if the content is loaded dynamically? If this is a good approach, is it better to load all the tabs on startup, or each time the tab is shown? (perhaps pros/cons if it's not totally obvious which is better in most/all cases)

Solution

You can use either Frames or Forms.

With Frames you have to add a TabControl as the parent for each Frame.
With Forms you have to dock each Form to the PageControl (the Form caption will automatic be the TabControl Caption).

procedure TMyForm.AddPage( AFormClass : TFormClass );
var
  LForm : TForm;
begin
  LForm := AFormClass.Create( Self );
  LForm.ManualDock( PageControl1, nil, alClient );
  LForm.Show;
end;

Example

Create a base Settings Form

unit UI_Form_SettingBase;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs;

type
  TUISettingBase_Form = class( TForm )
  private

  protected
    procedure DoSaveData; virtual;
  public
    function CanSaveData : Boolean; virtual;
    procedure SaveData;
  end;

  TUISettingBase_FormClass = class of TUISettingBase_Form;

var
  UISettingBase_Form : TUISettingBase_Form;

implementation

{$R *.dfm}
{ TUISettingBase_Form }

function TUISettingBase_Form.CanSaveData : Boolean;
begin
  Result := True;
end;

procedure TUISettingBase_Form.DoSaveData;
begin

end;

procedure TUISettingBase_Form.SaveData;
begin
  if CanSaveData
  then
    DoSaveData;
end;

end.

Derive all Settings Forms from that Form and override the DoSaveData and optionally the CanSaveData methods

Common Settings (with a simple CheckBox)

unit UI_Form_SettingCommon;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, UI_Form_SettingBase, Vcl.StdCtrls;

type
  TUISettingCommon_Form = class(TUISettingBase_Form)
    CheckBox1: TCheckBox;
  private

  protected
    procedure DoSaveData; override;
  public

  end;

var
  UISettingCommon_Form: TUISettingCommon_Form;

implementation

{$R *.dfm}

procedure TUISettingCommon_Form.DoSaveData;
begin
  inherited;
  // code to save the data
end;

end.

Connection Settings (with a simple Edit control)

unit UI_Form_SettingConnection;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, UI_Form_SettingBase, Vcl.StdCtrls;

type
  TUISettingConnection_Form = class( TUISettingBase_Form )
    Edit1 : TEdit;
  private
  protected
    procedure DoSaveData; override;
  public
  end;

var
  UISettingConnection_Form : TUISettingConnection_Form;

implementation

{$R *.dfm}
{ TUISettingConnection_Form }

procedure TUISettingConnection_Form.DoSaveData;
begin
  inherited;
  // code to save the data
end;

end.

Putting the pieces together: The real Settings Form

The main Setting Form is also derived from the SettingBase

unit UI_Form_Settings;

interface

uses
  System.Generics.Collections,
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, UI_Form_SettingBase, Vcl.StdCtrls,
  Vcl.ExtCtrls, Vcl.ComCtrls;

type
  TUISettings_Form = class( TUISettingBase_Form )
    PageControl1 : TPageControl;
    Panel1 : TPanel;
    Save_Button : TButton;
  private
    FForms : TList<TUISettingBase_Form>;
    procedure AddSettingPage( ASettingFormClass : TUISettingBase_FormClass );
  protected
    procedure DoSaveData; override;
  public
    function CanSaveData : Boolean; override;
    procedure AfterConstruction; override;
    procedure BeforeDestruction; override;
  end;

var
  UISettings_Form : TUISettings_Form;

implementation

{$R *.dfm}

uses
  UI_Form_SettingCommon, UI_Form_SettingConnection;
{ TUISettings_Form }

procedure TUISettings_Form.AddSettingPage( ASettingFormClass : TUISettingBase_FormClass );
var
  LForm : TUISettingBase_Form;
begin
  LForm := ASettingFormClass.Create( Self );
  try
    LForm.ManualDock( PageControl1, nil, alClient );
    LForm.Show;
    FForms.Add( LForm );
    LForm := nil;
  finally
    LForm.Free;
  end;
end;

procedure TUISettings_Form.AfterConstruction;
begin
  inherited;
  FForms := TList<TUISettingBase_Form>.Create;
  // add all the setting forms
  AddSettingPage( TUISettingCommon_Form );
  AddSettingPage( TUISettingConnection_Form );
end;

procedure TUISettings_Form.BeforeDestruction;
begin
  inherited;
  FForms.Free;
end;

function TUISettings_Form.CanSaveData : Boolean;
var
  LForm : TUISettingBase_Form;
begin
  // iterate all setting forms if they can save the data
  Result := True;
  for LForm in FForms do
    Result := Result and LForm.CanSaveData;
end;

procedure TUISettings_Form.DoSaveData;
var
  LForm : TUISettingBase_Form;
begin
  inherited;
  // iterate all setting forms and save the data
  for LForm in FForms do
    LForm.SaveData;
end;

end.