Choose MainForm from a list of available forms

Question

Is it possible to choose a form (as a mainform) from a list of \"available\" forms after connecting to the database ? I have a datamodule with 3 \'available\' forms.No mainform

Answer 1

You can easily do something like that in the DPR.

program Project1;

uses
  Forms,
  Unit1 in 'Unit1.pas' {Form1},
  Unit2 in 'Unit2.pas' {DM1: TDataModule},
  Unit3 in 'Unit3.pas' {Form2};

{$R *.res}

begin
  Application.Initialize;
  Application.CreateForm(TDM1, DM1);
  case DM1.ChooseForm of
    1: Application.CreateForm(TForm1, Form1);
    else Application.CreateForm(TForm2, Form2);
  end;
  Application.Run;
end.

In this example you first create the datamodule. When it's created you can use the logic in the datamodule. In the datamodule I made a public function that returns an integer to determine which form to load. (In practice I would not rely on magic numbers)

Answer 2

The main form is deemed to be the first form created by a call to Application.CreateForm. So add your selection logic to the .dpr file code, and then call Application.CreateForm to create whichever form the user selects.

// .dpr code
begin
  Application.Initialize;
  CreateMainForm;
  Application.Run;
end.

Here, CreateMainForm is provided by you and implements the user form selection. It might go like this:

procedure CreateMainForm;
var
  Form: TForm;
  FormClass: TFormClass;
begin
  FormClass := ChooseMainFormClass;
  Application.CreateForm(FormClass, Form);
end;

Again, ChooseMainFormClass is provided by you.