Choose MainForm from a list of available forms - delphi

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 for the time being.Datamodule is created first. Now, I would like to select the form depending on the database the user logs in to, and make it the mainform. Can this be done and how ?

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.