I'm building an application that contains around 30 Forms. I need to manage sessions, so I would like to have a global LoggedInUser variable accessible from all forms. I read "David Heffernan"'s post about global variables, and how to avoid them but I thought it would be easier to have a global User variable rather than 30 forms having their own User variable.

So i have a unit : GlobalVars

    unit GlobalVars;

    interface
    uses User; // I defined my TUser class in a unit called User
    var
       LoggedInUser: TUser;

    implementation

    initialization
       LoggedInUser:= TUser.Create;
    finalization
       LoggedInUser.Free;
    end.

Then in my LoginForm's LoginBtnClick procedure I do :

unit FormLogin;

interface

uses
  [...],User;

type
  TForm1 = class(TForm)
   [...]
    procedure LoginBtnClick(Sender: TObject);
  private
    { Déclarations privées }
  public
  end;

var
  Form1: TForm1;
  AureliusConnection : IDBConnection;

implementation

{$R *.fmx}
uses [...]GlobalVars;

procedure TForm1.LoginBtnClick(Sender: TObject);
var
  Manager : TObjectManager;
  MyCriteria: TCriteria<TUser>;
  u : TUser;
begin
  Manager := TObjectManageR.Create(AureliusConnection);
   MyCriteria :=Manager.Find<TUtilisateur>
    .Add(TExpression.Eq('login',LoginEdit.Text))
    .Add(TExpression.Eq('password',PasswordEdit.Text));
  u := MyCriteria.UniqueResult;
  if u = nil then
   MessageDlg('Login ou mot de passe incorrect',TMsgDlgType.mtError,[TMsgDlgBtn.mbOK],0)
  else begin
   LoggedInUser:=u;     //Here I assign my local User data to my global User variable
   Form1.Destroy;
   A00Form.visible:=true;
  end;
  Manager.Free;
end;

Then in another form I would like to access this LoggedInUser object in the Menu1BtnClick procedure :

Unit C01_Deviations;

interface

uses
  System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants, 
  FMX.Types, FMX.Graphics, FMX.Controls, FMX.Forms, FMX.Dialogs, FMX.StdCtrls,
  FMX.ListView.Types, FMX.ListView, FMX.Objects, FMX.Layouts, FMX.Edit, FMX.Ani;

type
  TC01Form = class(TForm)
   [...]
Menu1Btn: TButton;
[...]
procedure Menu1BtnClick(Sender: TObject);

  private
    { Déclarations privées }
  public
    { Déclarations publiques }
  end;

var
  C01Form: TC01Form;

implementation
uses [...]User,GlobalVars;
{$R *.fmx}

procedure TC01Form.Menu1BtnClick(Sender: TObject);
var
  Assoc : TUtilisateur_FonctionManagement;
  ValidationOK : Boolean;
  util : TUser;
begin
  ValidationOK := False;
  util := GlobalVars.LoggedInUser; // Here i created a local user variable for debug purposes as I thought it would permit me to see the user data. But i get "Inaccessible Value" as its value
  util.Nom:='test';
  for Assoc in util.FonctionManagement do  // Here is were my initial " access violation" error occurs
  begin
    if Assoc.FonctionManagement.Libelle = 'Reponsable équipe HACCP' then
    begin
      ValidationOK := True;
      break;
    end;
  end;
  [...]
end;

When I debug I see "Inaccessible Value" in the value column of my user. Do you have any idea why ?

I tried to put an integer in this GlobalVar unit, and i was able to set its value from my login form and read it from my other form..

I guess I could store the user's id, which is an integer, and then retrieve the user from the database using its id. But it seems really unefficient.