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Bootstrapping

After creating our resolvers, type classes, and other business-related code, we need to make our app run. First we have to build the schema, then we can expose it with an HTTP server, WebSockets or even MQTT.

Create Executable Schema

To create an executable schema from type and resolver definitions, we need to use the buildSchema function. It takes a configuration object as a parameter and returns a promise of a GraphQLSchema object.

In the configuration object we must provide a resolvers property, which is supposed to be an array of resolver classes:

import { FirstResolver, SecondResolver } from "./resolvers";
// ...
const schema = await buildSchema({
  resolvers: [FirstResolver, SecondResolver],
});

Be aware that only operations (queries, mutation, etc.) defined in the resolvers classes (and types directly connected to them) will be emitted in schema.

So if we have defined some object types (that implements an interface type with disabled auto registering) but are not directly used in other types definition (like a part of an union, a type of a field or a return type of an operation), we need to provide them manually in orphanedTypes options of buildSchema:

import { FirstResolver, SecondResolver } from "../app/src/resolvers";
import { FirstObject } from "../app/src/types";
// ...
const schema = await buildSchema({
  resolvers: [FirstResolver, SecondResolver],
  // Provide all the types that are missing in schema
  orphanedTypes: [FirstObject],
});

In case of defining the resolvers array somewhere else (not inline in the buildSchema), we need to use the as const syntax to inform the TS compiler and satisfy the NonEmptyArray<T> constraints:

// resolvers.ts
export const resolvers = [FirstResolver, SecondResolver] as const;

// schema.ts
import { resolvers } from "./resolvers";

const schema = await buildSchema({ resolvers });

There are also other options related to advanced features like authorization or validation - you can read about them in docs.

To make await work, we need to declare it as an async function. Example of main.ts file:

import { buildSchema } from "type-graphql";

async function bootstrap() {
  const schema = await buildSchema({
    resolvers: [
      // ... Resolvers classes
    ],
  });

  // ...
}

bootstrap(); // Actually run the async function

Create an HTTP GraphQL endpoint

In most cases, the GraphQL app is served by an HTTP server. After building the schema we can create the GraphQL endpoint with a variety of tools such as graphql-yoga or @apollo/server.

Below is an example using @apollo/server:

import { ApolloServer } from "@apollo/server";
import { startStandaloneServer } from "@apollo/server/standalone";

const PORT = process.env.PORT || 4000;

async function bootstrap() {
  // ... Build GraphQL schema

  // Create GraphQL server
  const server = new ApolloServer({ schema });

  // Start server
  const { url } = await startStandaloneServer(server, { listen: { port: 4000 } });
  console.log(`GraphQL server ready at ${url}`);
}

bootstrap();

Remember to install the @apollo/server package from npm - it's not bundled with TypeGraphQL.

Of course you can use the express-graphql middleware, graphql-yoga or whatever you want 😉

Create typeDefs and resolvers map

TypeGraphQL provides a second way to generate the GraphQL schema - the buildTypeDefsAndResolvers function.

It accepts the same BuildSchemaOptions as the buildSchema function but instead of an executable GraphQLSchema, it creates a typeDefs and resolversMap pair that you can use e.g. with @graphql-tools/*`:

import { makeExecutableSchema } from "@graphql-tools/schema";

const { typeDefs, resolvers } = await buildTypeDefsAndResolvers({
  resolvers: [FirstResolver, SecondResolver],
});

const schema = makeExecutableSchema({ typeDefs, resolvers });

Or even with other libraries that expect the schema info in that shape, like apollo-link-state:

import { withClientState } from "apollo-link-state";

const { typeDefs, resolvers } = await buildTypeDefsAndResolvers({
  resolvers: [FirstResolver, SecondResolver],
});

const stateLink = withClientState({
  // ... Other options like `cache`
  typeDefs,
  resolvers,
});

// ... Rest of `ApolloClient` initialization code

There's also a sync version of it - buildTypeDefsAndResolversSync:

const { typeDefs, resolvers } = buildTypeDefsAndResolversSync({
  resolvers: [FirstResolver, SecondResolver],
});

However, be aware that some of the TypeGraphQL features (i.a. query complexity) might not work with the buildTypeDefsAndResolvers approach because they use some low-level graphql-js features.