typed-graphql-subscriptions

Type-safe PubSub wrapper for GraphQL subscriptions

Installation

npm install typed-graphql-subscriptions

Usage

Create a TypeScript type mapping the name of each PubSub channel to a Tuple that represents the arguments that will be passed to publish.

type Channels = {
  announcementCreated: [{ body: string }];
};

More commonly, you want to utilize a composite name for your channel where chatMessageReceived:42 and chatMessageReceived:43 are separate channels but share the same type for the payload. We can define the types for these channels like this:

type Channels = {
  announcementCreated: [{ body: string }];
  chatMessageReceived: [number, { body: string }];
};

Create a PubSub instance and pass it to TypedPubSub's contructor, making sure to include the generic type variable:

import { PubSub } from "graphql-subscriptions";
import { TypedPubSub } from "typed-graphql-subscriptions";

const pubSub = new PubSub();
const typedPubSub = new TypedPubSub<Channels>(pubSub);

Note: You can use any PubSub implementation you like (for example, this one), as long as it implements PubSubEngine.

Now you can safely invoke subscribe using either two or three arguments:

typedPubSub.publish("announcementCreated", {
  body: "Site is down for maintenance.",
});

typedPubSub.publish("chatMessageReceived", 42, { message: "Hello." });

The asyncIterator method is called similarly:

typedPubSub.asyncIterator("announcementCreated");

typedPubSub.asyncIterator("chatMessageReceived", 42);