Relationship Field

Example uses:

• To add Product documents to an Order document
• To allow for an Order to feature a placedBy relationship to either an Organization or User collection
• To assign Category documents to Post documents

* An asterisk denotes that a property is required.

Options can be dynamically limited by supplying a query constraint, which will be used both for validating input and filtering available relationships in the UI.

The filterOptions property can either be a Where query directly, or a function that returns one. When using a function, it will be called with an argument object with the following properties:

Example:

  const relationshipField = {
    name: 'purchase',
    type: 'relationship',
    relationTo: ['products', 'services'],
    filterOptions: ({ relationTo, siblingData }) => {
      // returns a Where query dynamically by the type of relationship
      if (relationTo === 'products') {
        return {
          'stock': { is_greater_than: siblingData.quantity }
        }
      }

      if (relationTo === 'services') {
        return {
          'isAvailable': { equals: true }
        }
      }
    },
  };

You can learn more about writing queries here.

Given the variety of options possible within the relationship field type, the shape of the data needed for creating and updating these fields can vary. The following sections will describe the variety of data shapes that can arise from this field.

Has One

The most simple pattern of a relationship is to use hasMany: false with a relationTo that allows for only one type of collection.

{
  slug: 'example-collection',
  fields: [
    {
      name: 'owner', // required
      type: 'relationship', // required
      relationTo: 'users', // required
      hasMany: false,
    }
  ]
}

The shape of the data to save for a document with the field configured this way would be:

  {
     // Mongo ObjectID of the related user
    "owner": "6031ac9e1289176380734024"
  }

When querying documents in this collection via REST API, you could query as follows:

?where[owner][equals]=6031ac9e1289176380734024.

Has One - Polymorphic

Also known as dynamic references, in this configuration, the relationTo field is an array of Collection slugs that tells Payload which Collections are valid to reference.

{
  slug: 'example-collection',
  fields: [
    {
      name: 'owner', // required
      type: 'relationship', // required
      relationTo: ['users', 'organizations'], // required
      hasMany: false,
    }
  ]
}

The shape of the data to save for a document with more than one relationship type would be:

  {
    "owner": {
      "relationTo": "organizations",
      "value": "6031ac9e1289176380734024"
    }
  }

Here is an example for how to query documents by this data (note the difference in referencing the owner.value):

?where[owner.value][equals]=6031ac9e1289176380734024.

You can also query for documents where a field has a relationship to a specific Collection:

?where[owners.relationTo][equals]=organizations.

This query would return only documents that have an owner relationship to organizations.

Has Many

The hasMany tells Payload that there may be more than one collection saved to the field.

{
  slug: 'example-collection',
  fields: [
    {
      name: 'owners', // required
      type: 'relationship', // required
      relationTo: 'users', // required
      hasMany: true,
    }
  ]
}

To save the to hasMany relationship field we need to send an array of IDs:

  {
    "owners": [ "6031ac9e1289176380734024", "602c3c327b811235943ee12b" ]
  }

When querying documents, the format does not change for arrays:

?where[owners][equals]=6031ac9e1289176380734024.

Has Many - Polymorphic

{
  slug: 'example-collection',
  fields: [
    {
      name: 'owners', // required
      type: 'relationship', // required
      relationTo: ['users', 'organizations'], // required
      hasMany: true,
      required: true,
    }
  ]
}

Relationship fields with hasMany set to more than one kind of collections save their data as an array of objects—each containing the Collection slug as the relationTo value, and the related document id for the value:

{
  "owners": [
    {
      "relationTo": "users",
      "value": "6031ac9e1289176380734024"
    }, {
      "relationTo": "organizations",
      "value": "602c3c327b811235943ee12b"
    }
  ]
}

Querying is done in the same way as the earlier Polymorphic example:

?where[owners.value][equals]=6031ac9e1289176380734024.