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belongs to associations

Overview​

Belongs to associations are to be used when the model in question is related to another model, and contains a foreign key to that model within its table. An example of a belongs to would be in the case of a User and Post model, where a User can write many Posts, and each Post would contain a field (called a foreign key) which points back to the id field of a User who owns it. In this context, we would say that the Post belongs to the User.

export default class Post extends Dream {
  ...
  @deco.BelongsTo('User')
  public user: User
  public userId: DreamColumn<User, 'userId'>
}

Options​

Optional​

BelongsTo associations are required by default (and should have a corresponding not-null declaration on the foreign key column). To make an association optional, pass the optional: true option (and ensure that the column allows null values).

export default class Post extends Dream {
  ...
  @deco.BelongsTo('User', { optional: true })
  public user: User
  public userId: DreamColumn<User, 'userId'>
}

Foreign key​

By default, the foreign key is derived from the association name. E.g., in the example below, the default foreign key would be userId. This can be overridden by including an explicit foreignKey: '<camelized-column-name-on-this-table>' option.

export default class Post extends Dream {
  public get table() {
    return 'posts' as const
  }

  public id: number
  public content: string | null

  @deco.BelongsTo('User', { foreignKey: 'myUserId' })
  public user: User
  public myUserId: number
}

Primary key override​

By default, the column that the foreign key points to is returned by the primaryKey getter (and defaults to id). For associations that point to something other than the primary key, this can be overridden by passing the primaryKeyOverride: '<column-name-on-target-table>' option.

export default class Post extends Dream {
  public get table() {
    return 'posts' as const
  }

  public id: number
  public content: string | null

  @deco.BelongsTo('User', { primaryKeyOverride: 'uuid' })
  public user: User
  public userId: number
}