Triggers

Triggers execute a function in response to a change in the database. This is achieved by decorating a function with the @trigger decorator within a class that extends the base SquidService class.

The following example shows a trigger that is executed on a user change to the users database collection:

Backend code

import { SquidService, trigger, TriggerRequest } from '@squidcloud/backend';

export class ExampleService extends SquidService {
  @trigger('userChange', 'users')
  async handleUserChange(request: TriggerRequest): Promise<void> {
    // TODO - add your business logic here
  }
}

If the function is triggered by a database other than the built-in database, then the integration ID must be specified as the third parameter in the @trigger decorator. For example:

Backend code

@trigger('userChange', 'User', 'HrDatabase')

The trigger takes the following parameters:

Name	Type	Description
id	string	The id of the trigger. Should be unique.
collectionName	string	The name of the collection to trigger on.
integrationId?	string	The id of the integration to trigger on. If not provided, the built_in_db integration is used.

The trigger request provides the folloing information on the change:

{
  squidDocId: SquidDocId; // the primary key for the document
  mutationType: MutationType; // the type of operation performed
  docBefore?: T; // the document's previous state
  docAfter?: T; // the document's updated state
}

To allow Squid to discover the trigger and the rest of the functions in the same service, make sure the service is exported in the service/index.ts file:

service/index.ts

export * from './example-service';

For more information, view the (API documentation)[https://docs.squid.cloud/docs/api-reference/backend-sdk-reference/exports#trigger] for the trigger decorator.