# relationshipReverse

Adding a relationshipReverse field to a doc type schema reveals Apostrophe docs that have established relationships with a given doc. It is a developer convenience, showing the receiving side of a relationship field. There is no editing interface for this field type as the relationship is defined in the paired relationship field.

Take the example of a website that has a pizza piece type with a relationship field connecting to its topping piece type. Each pizza piece chooses the registered toppings that it has (the relationship is pizza-to-topping). The website might also want to list all available toppings on a page and show all pizzas that use each topping (the topping-to-pizza direction). A relationshipReverse field could make it easy to find and display that information.

# Module field definition

The field name must begin with an underscore (_). This indicates that the ultimate value is not stored in the database, but is populated when needed.

// Configuring the `_pizzas` field in a module's `fields.add` subsection:
_pizzas: {
  type: 'relationshipReverse',
  withType: 'pizza',
  reverseOf: '_toppings'

# Settings

# Required

Property Type Default Description
type String n/a Specifies the field type (relationshipReverse for this type)

# Optional

Property Type Default Description
reverseOf String n/a Set to the name of the related relationship field.
ifOnlyOne Boolean false If true, it will only reveal the relationship data if the doc query returned only one document. See below for more.
withType String Uses the field name, minus its leading _ and possible trailing s The name of the related type.
readOnly Boolean false If true, prevents the user from editing the field value


For relationships with pages, use withType: '@apostrophecms/any-page-type'.

If withType is not set the name of the field must match the name of the related type, with a leading _ (underscore), and optional trailing s added (e.g., _article or _articles to connect to the article piece type).

# ifOnlyOne

The ifOnlyOne option can provide a performance improvement if the reverse relationship data is only needed when one piece is queried. For example, in the example above, the pizza relationship data may be only needed on a topping show page, where only one topping is displayed; not on the index page, where many toppings are listed.

Setting ifOnlyOne: true tells Apostrophe not to look for the extra relationship data in those contexts, such as index pages, where many pieces are queried.