MorphTo Relationship

The MorphTo relationship represents the inverse of a polymorphic relationship, where the current (child) model stores the type and ID of the related parent model.

Explanation

For example, a Comment or Image might belong to either a Post or a Video as its parent. The child stores *_type and *_id fields:

Defining the Relationship

Define MorphTo on the child, specifying the type and id keys:

relationships: {
  parent: [MorphTo, 'commentable_type', 'commentable_id']
}

• The first argument is the type key on the child (e.g., 'commentable_type').
• The second is the id key on the child (e.g., 'commentable_id').

Example

{
  models: {
    comment: {
      schema: '++id,body,commentable_id,commentable_type',
      properties: ['id', 'body', 'commentable_id', 'commentable_type'],
      primaryKey: 'id',
      relationships: {
        parent: [MorphTo, 'commentable_type', 'commentable_id'],
      },
    },
    image: {
      schema: '++id,url,imageable_id,imageable_type',
      properties: ['id', 'url', 'imageable_id', 'imageable_type'],
      primaryKey: 'id',
      relationships: {
        parent: [MorphTo, 'imageable_type', 'imageable_id'],
      },
    },
    post: {
      schema: '++id,title',
      properties: ['id', 'title'],
      primaryKey: 'id',
      relationships: {},
    },
    video: {
      schema: '++id,url',
      properties: ['id', 'url'],
      primaryKey: 'id',
      relationships: {},
    },
  }
}

Note

MorphTo is used on the child model to point to a parent of varying type, using the type and id keys stored on the child.