BelongsTo Relationship

The BelongsTo relationship represents an inverse one-to-one or many-to-one relationship where the current model holds a reference to another model.

Explanation

For example, a Profile belongs to a User:

Defining the Relationship

The relationship is defined in your model configuration under the relationships property as a tuple:

[BelongsTo, foreignModelTable: string, foreignKey: string, originatingPrimaryKey?: string, foreignPrimaryKey?: string]

Required Parameters

• BelongsTo: The relationship type
• foreignModelTable: The table name of the related model
• foreignKey: The foreign key in the current model that references the related model

Optional Parameters

• originatingPrimaryKey: The primary key in the current model (defaults to 'id')
• foreignPrimaryKey: The primary key in the foreign model (defaults to 'id')

Example

{
  models: {
    users: {
      schema: '++id, email, createdAt, updatedAt',
      properties: ['id', 'email', 'password'],
      primaryKey: 'id',
    },
    profiles: {
      schema: '++id, user_id, full_name, avatar_url', 
      properties: ['id', 'user_id', 'full_name', 'avatar_url'],
      relationships: {
        user: [BelongsTo, 'users', 'user_id'], 
      }
    }
  }
}

In this example:

• The Profile model has a user_id foreign key that references the User model's id
• The relationship is defined as [BelongsTo, 'users', 'user_id'] where:
  • 'users' is the foreignModelTable
  • 'user_id' is the foreignKey
  • The primary keys default to 'id' since they're not specified

Accessing the Relationship

// Get the profile's user
const profile = await Profile.find(1)
const user = await profile.user 

// The relationship is reactive
profile.user.onChange((newUser) => { 
  console.log('User updated:', newUser)
})

// You can also eager load the relationship
const profiles = await Profile.query()
  .with('user') 
  .fetch()