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Models & Codegen

Models are the heart of your application. In Ormed, models are simple Dart classes annotated with @OrmModel.

Prerequisites​

What You’ll Learn​

  • How to define core domain models for the tutorial app
  • How relations are expressed with Ormed annotations
  • How model definitions feed code generation

Step Outcome​

By the end of this page, you should have:

  • Genre and Movie model classes with relation metadata
  • Generated ORM artifacts (*.orm.dart) for query/repository usage
  • Generated DTOs used by seeders and HTTP handlers

Model Rules Used In This Tutorial​

  • Keep model classes declarative: fields + annotations only.
  • Put relation metadata on ignored fields (@OrmField(ignore: true)).
  • Use generated DTOs for writes (InsertDto/UpdateDto) instead of ad-hoc maps in handlers.

Define the models​

We'll define two models: Genre and Movie.

The Genre Model​

The Genre model represents a category of movies. It uses an auto-incrementing integer as its primary key.

@OrmModel(table: 'genres')
class Genre extends Model<Genre> {
  const Genre({
    required this.id,
    required this.name,
    this.description,
    this.createdAt,
    this.updatedAt,
  });

  @OrmField(isPrimaryKey: true, autoIncrement: true)
  final int id;

  final String name;
  final String? description;
  final DateTime? createdAt;
  final DateTime? updatedAt;
}

The Movie Model​

The Movie model represents a film. It has a relationship with Genre.

Key annotations used here:

  • @OrmModel(table: 'movies'): Maps the class to the movies table.
  • @OrmField(isPrimaryKey: true, autoIncrement: true): Defines the primary key.
  • @OrmRelation.belongsTo: Defines a "Many-to-One" relationship. We mark the field with @OrmField(ignore: true) because the relationship itself isn't a column; the genre_id foreign key is.
  const Movie({
    required this.id,
    required this.title,
    required this.releaseYear,
    this.summary,
    this.posterPath,
    this.genreId,
    this.createdAt,
    this.updatedAt,
  });

  @OrmField(isPrimaryKey: true, autoIncrement: true)
  final int id;

  final String title;
  final int releaseYear;
  final String? summary;
  final String? posterPath;
  final int? genreId;
  @OrmField(ignore: true)
  @OrmRelation.belongsTo(target: Genre, foreignKey: 'genre_id')
  final Genre? genre = null;

  final DateTime? createdAt;
  final DateTime? updatedAt;

Generate ORM code + DTOs​

Ormed uses code generation to provide type-safe queries and Data Transfer Objects (DTOs). Run the following command to generate the necessary code:

dart run build_runner build --delete-conflicting-outputs

What Gets Generated?​

When you run build_runner, Ormed generates several artifacts:

  1. Type Aliases ($Movie, $Genre): These are type aliases used with Ormed's query builder. When you call dataSource.query<$Movie>(), you're telling Ormed which model you want to query.

  2. Insert DTOs (MovieInsertDto): Used for creating new records. Only includes fields that should be set during creation.

  3. Update DTOs (MovieUpdateDto): Used for updating existing records. All fields are optional, so you only update what changes.

  4. ORM Registry: A central registry that maps all your models to their table definitions.

Why DTOs?​

The generator creates specialized DTOs like MovieInsertDto and MovieUpdateDto. We use these for database operations instead of the main model classes. This provides several benefits:

  1. Clarity: It's clear which fields are required for an insert vs. an update.
  2. Safety: You can't accidentally try to update a primary key or a read-only field.
  3. Validation: DTOs can have their own validation logic.

Verify Before Continuing​

You should now see generated files beside your models (for example movie.orm.dart, genre.orm.dart) and no analyzer errors.