GraphQL returning null

Question

I am trying to make a simple modularized Node.js application using GraphQL to learn it a little bit. I implemented a couple of types and tried to play with them in the GraphiQL without much success. Here is a minimal non-working example. MDC.js:

//MDC.js
module.exports.typeDef = `
    type MDC {
        getAll: String
        getWithInitials(initials: String): [String]
    }
`;

module.exports.resolvers = {
    MDC: {
        getAll: function() {
            return "get all called";
        },
        getWithInitials: function(initials) {
            return "get with initials called with initials = " + initials;
        }
    }
};

Schemas.js:

//schemas.js
const MDC = require('./mdc').typeDef; 
const MDCResolvers = require('./mdc').resolvers; 

const Query = `
  type Query {
    mdc: MDC
    hello: String
  }
`;


const resolvers = {
    Query: { 
        mdc: function() {
            return "mdc called (not sure if this is correct)"
        }
    },
    MDC: {
        getAll: MDCResolvers.MDC.getAll,
        getInitials: MDCResolvers.MDC.getWithInitials,
    },
    hello: function() {
        return "ciao"
    }
};

module.exports.typeDefs = [ MDC, Query ];
module.exports.resolvers = resolvers;

Server.js:

//server.js
const express        = require('express');
const app            = express();
var graphqlHTTP      = require('express-graphql');
var { buildSchema }  = require('graphql');

const port = 8000;
const schemas = require('./app/schemas/schemas');

require('./app/routes')(app, {});

var fullSchemas = "";
for(var i = 0; i < schemas.typeDefs.length; i ++){
  fullSchemas +=  "," + schemas.typeDefs[i];
}

console.log(schemas.resolvers) //I can see the functions are defined

var schema = buildSchema(fullSchemas);

var root = schemas.resolvers;


app.use('/graphql', graphqlHTTP({
  schema: schema,
  rootValue: root,
  graphiql: true,
}));

app.listen(port, () => {
  console.log('We are live on ' + port);
});

When in GraphiQL, if I call { hello } I correctly see as result { data : hello: "ciao"} } but when I try the following:

{
  mdc {
    getAll
  }
}

The result is null:

{
  "data": {
    "mdc": null
  }
}

I really do not understand what is wrong. I think it may be something related with how the type Query is defined (mostly because I do not understand its purpose) but maybe I have something wrong somewhere else.

Thank you!!

score 1 · Accepted Answer · answered Oct 15 '18 at 13:14

I thing, that is corect:

// schemas.js
const resolvers = {
    Query: {
        mdc: function() {
            return "mdc called (not sure if this is correct)"
        }
    },
    mdc: {
        getAll: MDCResolvers.MDC.getAll,
        getInitials: MDCResolvers.MDC.getWithInitials,
    },
    hello: function() {
        return "ciao"
    }
};

When you call

{
    mdc {
        getAll
    } 
}

answer is

{
    "data": {
        "mdc": {
            "getAll": "get all called"
        }
    }
 }

GraphQL returning null

1 Answers1