GraphQL。 如何编写解析器

Question

I just started to get into GraphQL. I am using GraphQL.js and express. Right now I am trying to build a simple example using a hardcoded JSON as the data in my javascript file. I then want to use express middleware to listen to HTTP requests via curl or insomnia. In the middleware I want to extract the query using body-parser. Right now I am having trouble with resolvers.

Please have a look at my code.

var express = require('express');
var graphqlHTTP = require('express-graphql');
var { buildSchema, graphql } = require('graphql');
var bodyParser = require('body-parser');

var schema = buildSchema(`
  type Product {
    name: String!
    price: Int!
  }

  type Query {
    product(name: String): Product
  }
`);

var products = {
  'Mango': {
    name: 'Mango',
    price: 12,
  },
  'Apfel': {
    name: 'Apfel',
    price: 3,
  },
};

resolvers = {
  Query: {
    product: (root, { name}) => {
      return products[name];
    },
  },
};

var app = express();
app.use(bodyParser.text({ type: 'application/graphql' }));

app.post('/graphql', (req, res) => {
  graphql(schema, req.body)
  .then((result) => {
    res.send(JSON.stringify(result, null, 2));
  });
});

app.listen(4000);

This does not work. When I post a query using curl with

curl -XPOST -H "Content-Type: application/graphql" -d "{product(name: \\"Apfel\\"){name price}}" http://localhost:4000/graphql

I get the response {"data". {"product": null}}. The resolver doesn't get called. How can I do this correctly?

Answer 1

Can you try this?

 var resolvers = { product: (args) => { return products[args.name]; }, }; app.post('/graphql', (req, res) => { graphql(schema, req.body, resolvers) .then((result) => { res.send(JSON.stringify(result, null, 2)); }); }); 

I think this can solve your issue

Answer 2

I recomend watching FunFunFunction series episode focused on GraphQl: GraphQl Basics

All of his episodes are quite interesting (and really fun)...