How to make custom type with definite value in gra

Question

This is the first time I am using graphQL, I have two questions related to it.

I have vaguely gone through the docs and was building something of my own.

So, My setup right now is very simple. In the starting point of my app, I have something like this

const express = require('express')
const app = express();
const graphqlHTTP = require("express-graphql")
const schema = require('./schema/schema')

app.use("/graphql", graphqlHTTP({
  schema: schema
}));

app.get('/', (req, res) => {
  res.json({"message": "Welcome to EasyNotes application. Take notes quickly. Organize and keep track of all your notes."});
});


//Listen to specific post 
app.listen(4000, () => {
  console.log("Listening for request on port 4000")
});

And my Schema looks like this

const graphql = require("graphql")

const { 
  GraphQLObjectType, 
  GraphQLString, 
  GraphQLSchema,
  GraphQLList,
  GraphQLID,
  GraphQLNonNull,
  GraphQLInt
  } = graphql


const GenderType = new GraphQLObjectType({
  name: 'Gender',
  fields: () => ({
    male: {

    }
  })
})


  const UserType = new GraphQLObjectType({
    name: 'User', // Importance of Name here
    fields: () => ({
      id: {
        type: GraphQLID
      },
      name: {
        type: GraphQLString
      },
      gender: {
        type: GenderType // Create custom type for it later
      }
    })
  })

In my above code snippet, Inside UserType I want my GenderType to be either male or female. How would write my custom type such that it only accepts value 'male' or 'female'?

Answer 1

What you want to do can be achieved with both Scalar Types and Enum Types. In your case you probably want to go with an enum because you have a small finite list of allowed values. Using the Enum Type will show the allowed values in the documentation in GraphiQL. In most GraphQL APIs Enum values use all capital values but you could use the value property to transparently map the female value to FEMALE. This would for example allow you to treat the values as lower case on the server side (we do this a lot because the values come in lower case from our postgres). Here some code for inspiration:

const GenderType = new GraphQLEnumType({
  name: 'Gender',
  values: {
    FEMALE: {
      value: 'female'
    },
    MALE: {
      value: 'male'
    }
  }
});