I am new to GraphQL. As an experiment, I ran the following Node.js Express server:
var express = require('express');
var { graphqlHTTP } = require('express-graphql');
var { buildSchema } = require('graphql');
var schema = buildSchema(`
type Student {
sid: ID,
name: String,
subjects: [String!],
address: Location
}
type Location{
unit: String,
city: String,
country: String,
postCode: Int
}
`);
var root = { // The root provides a resolver function for each API endpoint
address: () => ({
city: ()=>'London'
}),
};
var app = express();
app.use('/graphql', graphqlHTTP({
schema: schema,
rootValue: root,
graphiql: true,
}));
app.listen(4000);
console.log('Running a GraphQL API server at http://localhost:4000/graphql');
When I ran the following query on the interface on a browser:
{
address {
city
}
}
I got an error:
{
"errors": [
{
"message": "Query root type must be provided."
}
]
}
What should be the correct way of doing this?
CodePudding user response:
It turned out that I must define the schema 'Query' (and optionally 'Mutation') for the entry point.
var express = require('express');
var { graphqlHTTP } = require('express-graphql');
var { buildSchema } = require('graphql');
var fakeDatabase = [{sid:parseInt(Math.random()*10000),
name:'Philip',
subjects:['Chemistry', 'Physics', 'Maths'],
address:{
unit: 'H505',
city: 'London',
country: 'United Kingdom',
postCode: 33100
}}];
// 'Query' and 'Mutation' are special schemas defining the entry points
var schema = buildSchema(`
type Query {
name: String
sid(year: Int): ID
subjects: [String]
address: Location
}
type Location{
unit: String
city: String
country: String
postCode: Int
}
type Mutation{
setName(nn: String): String
}
`);
// Each field is either a constant or a callback
var root = {
name: ()=>fakeDatabase[0].name,
sid: arg => (arg.year "-" fakeDatabase[0].sid),
subjects: fakeDatabase[0].subjects,
address: () => ({
city: ()=>fakeDatabase[0].address.city
}),
setName: arg => {fakeDatabase[0].name=arg.nn; return arg.nn;}
};
var app = express();
app.use('/graphql', graphqlHTTP({
schema: schema,
rootValue: root,
graphiql: true,
}));
app.listen(4000);
console.log('Running a GraphQL API server at http://localhost:4000/graphql');