Subscriptions — GraphQL · NestJS

Push changes to clients as they happen: a PubSub provider, mutations that publish, a subscription that filters what each subscriber receives and one that turns a payload into a sentence, graded by specs that subscribe through the schema.

What you will learn

Read the theory for Subscriptions

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Read-only: these tests are the lesson's contract. Make them pass by changing the code they test.

What you'll learn

  • Explain subscriptions: a long-lived operation that receives an event each time the server publishes one, usually over WebSockets
  • Publish events with a PubSub injected as a provider, and subscribe to them with @Subscription() returning its async iterator
  • Deliver an event only to the subscribers who want it with a filter over the payload and the subscription's variables
  • Shape what subscribers receive with resolve, and test subscriptions through the schema with graphql's subscribe()