intraweb-patterns

Intraweb Patterns — Rules

When developing a native web application in Delphi using the Intraweb framework, you are working with a stateful environment for the browser hosted by multiple isolated threads. Strictly apply the guidelines below.

1. Concurrency and Sessions (UserSession)

• Rule: NEVER use global data (var located in interface or open Singleton instances) to cache online user data, credentials and ID. The application is Web/Stateful/Threaded, these variables will leak cross-session.
• Implementation: All transient state storage and logged-in identities must flow from or store in resident structures of the TIWUserSession mapped in the ServerController pool:

  //Safe example for logged in user request context:
  LUsuarioId := UserSession.GetLoggedUserID;
  

2. Asynchronous Forms (Async Events)

• Rule: Favor class events Async over traditional submissions (Postback).
• Implementation: Interceptions such as clicking on save, cancel or change data combos buttons must prioritize methods declared in asynchronous events (AJAX), mitigating reloading of the entire DOM:

  //Correct: Asynchronous Events (Ajax)
  procedure TIWFormClientes.iwBtnSalvarAsyncClick(Sender: TObject; EventParams: TStringList);
  begin
    //Database writes and color change in the local interface
    iwLblStatus.Caption := 'Salvo!';
  end;
  

3. Absence of Blocking Dialogs

• Rule: Do not use VCL Desktop synchronous mechanisms (ShowMessage, InputBox, Interactive Function Returns or exceptions that display visual Desktop errors across the system) in the Intraweb.
• Implementation: Trigger WebApplication.ShowMessage methods or callbacks and templates to guide User decisions via the frontend.

4. Business Rule Hiding (SRP)

• Rule: The TIWAppForm is the View (and loosely its controller/router). Business logic must NOT live in this TIWAppForm.pas.
• Implementation: The injectable model class, THouseService.Register(), manages rule manipulation calls clean of any connection with ServerController components - Returning abstract data capable of rendering in Forms.