Extending PageInfo / Connection

Bi-directional PageInfo

The Relay specs by default does not compute hasPreviousPage when paging forwards, and does not compute hasNextPage when paging forwards (see this issue for details) as it may be expensive to compute them. However, as many usecases of AutoRelay (mainly while fetching from a main database with limit/offset) do provide a very inexpensive way to compute that data, a biDirectionalPageInfo option has been created to allow calculating both those arguments from the first/last arguments and the entity count returned.

This option can be set globally or per query/field resolver

globally

new AutoRelayConfig({ pagination: { biDirectionalPageInfo: true } })

per query

@RelayedQuery(() => MyEntity, { biDirectionalPageInfo: true })
public async myEntities() {

}

Adding your own logic

AutoRelay allows extending PageInfo and Connection Objects with your own base classes. This can be useful for augmenting the Relay spec. The following example shows how to add a "totalCount" field containing the total number of items matching a paginated query

src/base-connection.ts

import { RelayNbOfItems } from 'auto-relay'

@ObjectType({ isAbstract: true })
export class BaseConnection {

  @Field(() => Int)
  public totalCount(
    @RelayNbOfItems() nbOfItem: number
  ): number {
    return nbOfItem;
  }

}

src/index.ts

new AutoRelayConfig({ extends: { connection: () => BaseConnection } })

this will result in all Connection objects being augmented with the totalCount field