this.findOneById is not a function (Apollo Server Express v4 GraphQL)

I have the following ApolloServer (v4)

import { MongoDataSource } from 'apollo-datasource-mongodb'

export default class LoaderAsset extends MongoDataSource {
 async getAsset(assetId) {
    return this.findOneById(assetId) // ERROR IS HERE
  }
}

async function startApolloServer(app) {
  const httpServer = http.createServer(app);
  
  const server = new ApolloServer({
    typeDefs,
    resolvers,
    plugins: [ApolloServerPluginDrainHttpServer({ httpServer })]
    
  });

  await server.start();
  app.use(
    '/graphql',
    cors(),
    bodyParser.json(),
    expressMiddleware(server, {
      context: async ({ req }) => {
       return {
        dataSources: {
          loaderAsset: new LoaderAsset(modelAsset),
        }
      }
      },
    }),
  );


  const port = config.get('Port') || 8081;
  await new Promise(resolve => httpServer.listen({ port }, resolve));
}

when I run graphql and send one assetId, everything is working till I get following error:

this.findOneById is not a function

By the way (this.) has collection and model objects but not any methods.

is it because apollo-datasource-mongodb is not compatible with the new version of apollo server v4?

[systemkrash]

what i did is i override my datasource class so I can call the initialize method inside in the MongoDatasource class. Now it works for me.

import { MongoDataSource } from 'apollo-datasource-mongodb';

class ReceptionDataSource extends MongoDataSource {
  constructor({ collection, cache }) {
    super(collection);
    super.initialize({ context: this.context, cache });
  }

  async getReception(receptionId) {
    return await this.findOneById(receptionId);
  }
}

export default ReceptionDataSource;

then in my context

async function startApolloServer(app) {
  const httpServer = http.createServer(app);
  
  const server = new ApolloServer({
    typeDefs,
    resolvers,
    plugins: [ApolloServerPluginDrainHttpServer({ httpServer })]
    
  });

  await server.start();
  app.use(
    '/graphql',
    cors(),
    bodyParser.json(),
    expressMiddleware(server, {
      context: async ({ req }) => {
      const { cache } = server
       return {
        dataSources: {
          loaderAsset: new ReceptionDataSource({collection: ReceptionModel, cache}),
        }
      }
      },
    }),
  );


  const port = config.get('Port') || 8081;
  await new Promise(resolve => httpServer.listen({ port }, resolve));
}

[systemkrash]

@systemkrash Thank you for your code snippet, it’s of great help! I’m still struggling with a point: How do you correctly set the context in the DataSource (with additional fields)?

super.initialize({ context: this.context, cache });

this.context is always undefined, isn’t it?

Also I’ll have a problem, even with a defined context. I was exploiting the fact that the dataSources context was containing the other dataSources and himself:

// inside any of my DataSource extended class

this.context.dataSources.users.findOneById(this.context.token)

EDIT: I got help from a member of ApolloGraphQL and found a way to set correctly the context and dataSources: apollographql/apollo-server#7096

I believed its not undefined because that attribute belongs to MongoDataSource class which we use to extend our own Datasource class. sorry for the late response.