dext-framework-patterns

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. Registration of Dependency Injection Services
  App.Services.AddSingleton<IEmailService, TEmailService>;
  App.Services.AddScoped<IOrderRepository, TOrderRepository>;

  //2. Route Mapping
  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' is populated via JSON from the request body automatically.
//'Database' is injected 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

//Typed path-based routing (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 is the Smart Property representation for the context class
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; //Use Task Flow from the central library

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).