belongsTo

The belongsTo association creates a relationship where the source model holds the foreign key that points to the target model.

In Sequelize terms, belongsTo is the “child → parent” side of the association. It is commonly paired with hasOne or hasMany on the other model.

Basic Example

@Table(tableName: 'posts')
abstract class Post {
  @PrimaryKey()
  @AutoIncrement()
  DataType id = DataType.INTEGER;

  static PostModel get model => PostModel();
}

@Table(tableName: 'post_details')
abstract class PostDetails {
  @PrimaryKey()
  @AutoIncrement()
  DataType id = DataType.INTEGER;

  // Foreign key column on the source model
  @ColumnName('post_id')
  DataType post_id = DataType.INTEGER;

  // Child -> Parent association
  @BelongsTo(Post, foreignKey: 'post_id', as: 'post')
  Post? post;

  static PostDetailsModel get model => PostDetailsModel();
}

Options

foreignKey

The foreign key column on the source model.

Example:

@BelongsTo(Post, foreignKey: 'post_id')
Post? post;

as

The association alias used by Sequelize (and by include helpers).

Example:

@BelongsTo(Post, as: 'post')
Post? post;

targetKey

By default, Sequelize references the target model’s primary key. You can override that by providing targetKey.

Example:

@BelongsTo(Post, foreignKey: 'post_id', targetKey: 'id')
Post? post;

Important note: If targetKey is the default ('id'), Sequelize already treats it as implicit. In our current generator we avoid explicitly sending targetKey: 'id' during association wiring because Sequelize may auto-create the inverse belongsTo when a hasOne/hasMany exists, and explicit default options can make the association “not reconcilable”.

Eager loading (include)

Generated models provide a type-safe include helper for belongsTo, the same way as hasOne and hasMany:

final details = await PostDetails.model.findOne(
  where: (c) => c.id.eq(1),
  include: (i) => [
    i.post(),
  ],
);

print(details?.post?.toJson());

Nested includes work as expected:

final details = await PostDetails.model.findOne(
  where: (c) => c.id.eq(1),
  include: (i) => [
    i.post(
      include: (postIncl) => [
        postIncl.user(),
      ],
    ),
  ],
);

Nested create

When creating an instance with nested association data, Sequelize requires the include tree to describe all nested levels you want it to accept.

Sequelize Dart’s generator builds the include tree for create calls so multi-level nested create payloads are not ignored.

Example (PostDetails → Post → User):

final details = await PostDetails.model.create(
  CreatePostDetails(
    post: CreatePost(
      title: 'Hello',
      user: CreateUsers(
        email: 'test@example.com',
        firstName: 'Test',
        lastName: 'User',
      ),
    ),
  ),
);

Instance methods (planned)

Sequelize supports instance methods for belongsTo such as getX, setX, and createX (see the Sequelize docs for details). We have generator code prepared for these methods, but but we're currently testing until the API is perfect.