Storage For Delphi Applications

Last Updated: 10/14/2005

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State Management
Storage For Delphi Applications
Complex State & Back Button

Safe Storage in IntraWeb for Delphi

Form / Datamodule Members

This section refers to IntraWeb for Delphi only: since IntraWeb forms and datamodules are persistent just like in a normal Delphi application you can store information as member variables and properties. Such members should be used when the form itself needs to store data about its instance or to receive input from another form.

User Session

The user session (covered more in detail in the Session Management section of this manual) contains a .Data property that can hold a reference to an object. When you need to store user specific information you can store it in the .Data property of the session. Data accepts a TObject instance and will destroy the TObject automatically when the session is destroyed. The easiest way is to create an object and add the fields that you wish, and then create your object and store it in the session's Data property when the session is created. The Phonetics demo shows an extended example of this.

When a new IntraWeb project is created a shell user session object is created for you in the ServerController. The default ServerController looks like this:

unit ServerController;
  unit ServerController;
 
interface
 
uses
  SysUtils, Classes, IWServerControllerBase,
  IWApplication, IWAppForm;
 
type
  TIWServerController = class(TIWServerControllerBase)
    procedure IWServerControllerBaseNewSession(ASession: TIWApplication;
      var VMainForm: TIWAppForm);
  private
  public
  end;
 
  TUserSession = class
  public
  end;
 
// Procs
  function UserSession: TUserSession;
 
implementation
{$R *.dfm}
 
uses
  IWInit;
 
function UserSession: TUserSession;
begin
  Result := TUserSession(RWebApplication.Data);
end;
 
procedure TIWServerController.IWServerControllerBaseNewSession(
  ASession: TIWApplication; var VMainForm: TIWAppForm);
begin
  ASession.Data := TUserSession.Create;
end;
 
end.

TUserSession is an empty session object that you can add members, properties and methods to. The code to create the TUserSession for each session is also created in the OnNewSession Event.

A function named UserSession also exists for easy access to the object. So if you changed the TUserSession declaration to the following:

TUserSession = class
  public
    Username: string;
    Password: string;
  end;

You could access these properties elsewhere in your code simply as shown here:

UserSession.Username := 'Joe';
LPassword := UserSession.Password;

If you do not need a user session you may choose to eliminate it from the code. It is not necessary and is part of the default template simply as a convenience.

The class type of TUserSession can be of any type. For projects that are generated with a datamodule the TUserSession is a descendant of TComponent and not TObject as shown here. TComponent allows the session to own components such as the datamodule and allows for easier cleanup.