Lambda Mutations - Graphql

Documentation
1

Schema

To set up a lambda mutation, first you need to define it on your GraphQL schema by using the @lambda directive.

For example, to define a lambda mutation for Author that creates a new author with a default reputation of 3.0 given just the name:

type Author {
    id: ID!
    name: String! @search(by: [hash, trigram])
    dob: DateTime
    reputation: Float
}
type Mutation {
    newAuthor(name: String!): ID! @lambda
}

Resolver

Once the schema is ready, you can define your JavaScript mutation function and add it as resolver in your JS source code. To add the resolver you can use either the addGraphQLResolvers or addMultiParentGraphQLResolvers methods.

For example, to define the JavaScript newAuthor() lambda function and add it as resolver:

async function newAuthor({args, graphql}) {
    // lets give every new author a reputation of 3 by default
    const results = await graphql(`mutation ($name: String!) {
        addAuthor(input: [{name: $name, reputation: 3.0 }]) {
            author {
                id
                reputation
            }
        }
    }`, {"name": args.name})
    return results.data.addAuthor.author[0].id
}
self.addGraphQLResolvers({
    "Mutation.newAuthor": newAuthor
})

Example

Finally, if you execute this lambda mutation a new author Ken Addams with reputation=3.0 should be added to the database:

mutation {
	newAuthor(name: "Ken Addams")
}

Afterwards, if you query the GraphQL database for Ken Addams, you would see:

{
	"getAuthor": {
			"name":"Ken Addams",
			"reputation":3.0
		}
}
This is a companion discussion topic for the original entry at https://dgraph.io/docs/graphql/lambda/mutation/