Apollo MongoDB Datasource Help

Help
1

Hello Guys? I have an issue with my code and you certainly know how to solve it. The problem is when i make a getCrypto query its returning nulls values. But my getCryptos function is working fine.
I would like to query my cryptos with with “code” param. For example. When i try to query with [code: “BTC”] variable im getting nulls results. I think the problem is with resolver or datasource. I just would like to query all results by code. Thank you.

ApolloServer

const schema = application.createSchemaForApollo();

    const apolloServer = new ApolloServer({ 
      schema,
      dataSources: () =>({
        cryptoAPI: new Cryptos(client.db('cryptoDB').collection('cryptos'))
      }),
      csrfPrevention: true,
      introspection: true,
      plugins: [
        // Install a landing page plugin based on NODE_ENV
        process.env.NODE_ENV === 'production'
          ? ApolloServerPluginLandingPageProductionDefault({
              graphRef: "Finbrothers@current",
              footer: false,
            })
          : ApolloServerPluginLandingPageLocalDefault(),
      ],
    })

My Datasource


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

export default class Cryptos extends MongoDataSource {
    getCrypto(code) {
      return this.findByFields(code);
      }

    getCryptos(fields = {}) {
        return this.findByFields(fields);
    
    }
}

My resolver


import { GraphQLScalarType } from 'graphql';

const dateScalar = new GraphQLScalarType({
  name: 'Date',
  description: 'Date custom scalar type',
  parseValue(value) {
    return new Date(value); // Convert incoming integer to Date
  },
});


export const CryptoResolver = {

    Date: dateScalar,
  
    Query: {
            getCrypto: (_, {code} , { dataSources }) => {
                return dataSources.cryptoAPI.getCrypto(code);

            },
            getCryptos: (_, __, { dataSources }) => {
                return dataSources.cryptoAPI.getCryptos();
                
            },
    }
}
2

Is your field called code in the datasource? if yes maybe

    getCrypto(code) {
        return this.findByFields({ code } ); // instead of this.findByFields(code);
      }

Hope it helps.

3

Hi Kheang. I did what you suggest but still the same null response like my printscreen.

getcryo
getcryo1768×891 101 KB

4

What does your DB look like?

5

Do you mean my DB schema?

dbschema
dbschema773×605 27.3 KB

6

Try to do some debugging.
console.log when you call getCrypto the code and see what is passed to the findByFields.
Try to hardcode findById with the actual _id of BTC to see if it pulls it correctly.

If I look at it rapidly, it looks fine, must be something that is not sent properly to your datasource maybe.

Add try / catch to see if you get any exceptions that aren’t displayed if you get to this point.

7

Hi Kheang. I finally found the bug. Everything was fine as you said. The problem was with Type query. I forgot to use on getCrypto. The wrong one was “getCrypto(code: String): Crypto” and the correct was getCrypto(code: String): [Crypto]. Just to community knows. Thanks again.

1 Like
8

Ahhhhhhh because it was findByFields which returns an array.
You could’ve kept `getCrypto(code: String): Crypto and just modify your resolver to return the first element it finds.

I didn’t catch that either!