Instance Method

join(_:on:)

.join(Foreign.self, on: databaseJoin)

@discardableResult func join<Foreign>(_ foreign: Foreign.Type, on join: DatabaseQuery.Join) -> Self where Foreign : Schema

Discussion

Joins against Foreign using the given join description.

In debug builds, the join is checked (when possible) to verify that it corresponds correctly to the provided model type; an assertion failure occurs if there is a mismatch. This check is not performed in release builds.

Warning

The space, schema, and alias specified by the join description must match the space, schema, and alias properties of the provided Foreign type. Violation of this rule will cause runtime errors in most kinds of queries, and incorrect data may be returned from queries which do run.

Tip

If you find that the requirements of your join are incompatible with this rule, you’re probably trying to do something that’s too complex for Fluent’s API to accomodate. The recommended solution is to bypass Fluent and execute the desired query more directly, either via SQLKit when working with an SQL database, or via MongoKitten if using MongoDB.