GraphQL- conditionally determine the type of a field in a schema

Question

I have the following mongoose schema:

const MessageSchema = new Schema({
    author: {
        account:{
           type:String,
           enum:['employee','admin'],
        },
    id: String,
    }
//other fields
})

Then in my graphql-schemas file, I have the following schema types:

const MessageType = new GraphQLObjectType({
     name: 'Message',
     fields: () => ({
        account: {
           type: AuthorType,
        //resolve method 
        },
        id: {type: GraphQLString},
   })
})

const AuthorType= new GraphQLObjectType({
   name: 'Author',
   fields: () => ({
     account: {
        type://This will either be AdminType or EmployeeType depending on the value of account in db (employee or admin),
        //resolve method code goes here
        }
})

})

As indicated in the comments of AuthorType , I need the account field to resolve to Admin or Employee depending on the value of the account field in the database. How do I conditionally determine the type of a field in a schema on the fly?

Answer 1

Instead of determining the type on the fly, I restructured my code as shown below:

const MessageType = new GraphQLObjectType({
    name: 'Message',
    fields: () => ({
       id:{type:GraphQLString},
        author: {
          type: AuthorType,
          async resolve(parent, args) {
            if (parent.author.account === 'guard') {
                return await queries.findEmployeeByEmployeeId(parent.author.id).then(guard => {
                    return {
                        username: `${guard.first_name} ${guard.last_name}`,
                        profile_picture: guard.profile_picture
                    }
                })
            } else if (parent.author.account === 'admin') {
                return {
                    username: 'Administrator',
                    profile_picture: 'default.jpg'
                }
            }
        }
    },
//other fields
   })
})

const AuthorType = new GraphQLObjectType({
    name: 'Author',
    fields: () => ({
       username: {type: GraphQLString},
       profile_picture: {type: GraphQLString},
  })
 })

Since all I need from the AuthorType is the author's username and profile picture, both employee and administrator have these fields, which I pass to AuthorType . In MessageType , I apply the logic to determine account type in the resolve method of author , then construct custom object out of the logic, to match AuthorType .