Dext Framework Patterns (Delphi)

The Dext Framework is a complete ecosystem for Delphi, directly inspired by ASP.NET Core and Spring Boot. It is intended for high-performance corporate development. Unlike Horse or DMVC, Dext embraces Dependency Injection, Minimal APIs with automatic model binding and has its own Entity ORM (

Dext.Entity

).

This manual provides the conventions that must be followed by the AI ​​when coding with Dext.

Important Note: Dext Framework is not short for DevExpress/DevExtreme visual components, but rather the backend project (https://github.com/cesarliws/dext).

Core Principles

1. Minimal Routing (Minimal APIs): Do not use traditional MVC Controllers unless necessary. Use functional routing syntax (

   MapGet

   ,

   MapPost

   ).
2. Auto Model Binding: Get JSON body not via strings and partial conversions, but by delegating strong typing to anonymous route parameters (

   function(Dto: MyDto): IResult

   ).
3. Integrated DI Container: All interface dependencies must be resolved via

   App.Services

   (Injection). Do not use manual factories.
4. Smart ORM (Dext.Entity): Never concatenate SQL.

---

1. WebApp Lifecycle and DI

Bootstrap of a Dext API occurs by registering services in the same route pipeline.

program MyAPI;

uses Dext.Web, Services.Interfaces, Services.Implementations;

begin
  var App := WebApplication;
  var Builder := App.Builder;

  // 1. Registro de Serviços de Injeção de Dependências
  App.Services.AddSingleton<IEmailService, TEmailService>;
  App.Services.AddScoped<IOrderRepository, TOrderRepository>;

  // 2. Mapeamento de Rotas
  Builder.MapGet<IResult>('/health', 
    function: IResult
    begin
        Result := Results.Ok('{"status": "ok"}');
    end);

  // 3. Start
  App.Run(8080);
end.

---

2. Minimal APIs & Model Binding

The preferred way to build REST APIs with Dext is using typed anonymous delegates, with DI dependencies passed in the final arguments.

Create user (Post + DTO Body + Auth)

type
  TCreateUserDto = record
    Name: string;
    Age: Integer;
  end;

// 'Dto' é populado via JSON do corpo da requisição automaticamente.
// 'Database' é injetado via DI.
Builder.MapPost<TCreateUserDto, IDatabaseService, IResult>('/users',
  function(Dto: TCreateUserDto; Database: IDatabaseService): IResult
  begin
    if Dto.Name.IsEmpty then
        Exit(Results.BadRequest('Name is required'));

    Database.SaveUser(Dto.Name, Dto.Age);
    
    Result := Results.Created('/users/new', 'User Created');
  end);

Path Params & Query

// Roteamento path-based tipado (Route parameter Binding)
Builder.MapGet<Integer, IResult>('/orders/{id}',
  function(Id: Integer): IResult
  begin
    var Order := FindOrder(Id);
    if Order = nil then
      Result := Results.NotFound
    else
      Result := Results.Ok(Order);
  end);

---

3. Dext.Entity (ORM & Smart Properties)

Database mapping with Dext is focused on strongly typed query building and "Code First" Classes.

LINQ-Like Queries

Avoid using complex RTTI or native ADOTables if you are on Dext. Deliver results in typed Collections (

IList<T>

).

uses Dext.Entity;

// P é a representaction da Smart Property para a classe de contexto
var Products := DbContext.Products
  .Where((P.Price > 100) and (P.Stock > 0))  // 'and' bitwise/Smart property syntax
  .OrderBy(P.Name)
  .Take(10)
  .ToList;

Understanding "Mass Update" via Dext.Entity

With Dext ORM, Updates can run in the database without pulling data into memory (as done in modern Entity Framework Core):

DbContext.Orders
  .Where(O.Status = 'Pending')
  .Update
  .Execute;

---

4. Returns (IResult)

Always return

IResult

-based implementations on endpoints using the

Results

factory.

• Results.Ok( MeuRecord )

  -> Status 200 + Automatically Serializes into JSON.

• Results.Created('/rota', 'Msg')

  -> Status 201 + Header "Location".

• Results.NotFound

  -> Status 404.

• Results.BadRequest('Msg')

  -> Status 400 bad request error.

---

5. Dext.Net Async Tasks and Resilience (TAsyncTask)

Dext includes more modern promises/tasks primitives than the pure

TTask

originals of Delphi.

uses Dext.Core.Tasks; // Usar Task Flow da biblioteca central

TAsyncTask.Run<TUserProfile>(
  function: TUserProfile
  begin
    Result := ExternalService.Call();
  end)
  .OnComplete( // Callback chamado no contexto Sincrono/Main thread.
    procedure(Profile: TUserProfile)
    begin
        ShowVclMessage(Profile.Name);
    end)
  .OnException(
    procedure(Ex: Exception)
    begin
       LogError(Ex.Message);
    end)
  .Start;

---

Review Checklist (Dext Framework)

• Fluent routes? Does the application use

  Builder.MapGet

  /

  MapPost

  with implicit binding instead of manual request manipulation and pure Body parse for complex json objects?
• Has the DI container been powered? Are instances being passed to constructors/routers through

  App.Services

  ?
• No Filter Strings in Data Modules? Did you use expressive Smart Properties (

  .Where(E.Price > 100)

  ) instead of query concat?
• Are returns based on records and POLD objects? (Plain Old Delphi Objects, allowing UTF-8 Zero Allocation JSON from Dext).