Common Resolver Patterns

This tutorial gives an overview about common scenarios you might encounter when implementing your GraphQL server with graphql-yoga and Prisma.

Note that all scenarios in this tutorial are based on the typescript-basic GraphQL boilerplate project.

Scenario: Add a new field to the data model and expose it in the API

Adding a new address field to the User type in the database, with the purpose of exposing it in the application API as well.

Instructions

1. Adding the field to the data model

in database/datamodel.graphql:

type User {
  id: ID! @unique
  email: String! @unique
  password: String!
  name: String!
  posts: [Post!]!
+ address: String
}

2. Deploying the updated data model

prisma deploy

This will...

• ... deploy the new database structure to the local service
• ... download the new GraphQL schema for the database to database/schema.graphql

3. Adding the field to the application schema

In src/schema.graphql:

type User {
  id: ID!
  email: String!
  name: String!
  posts: [Post!]!
+ address: String
}

Scenario: Adding a new resolver

Suppose we want to add a custom resolver to delete a Post.

Instructions

Add a new delete field to the Mutation type in src/schema.graphql

type Mutation {
  createDraft(title: String!, text: String): Post
  publish(id: ID!): Post
+ delete(id: ID!): Post
}

Add a delete resolver to Mutation part of src/index.js

delete(parent, { id }, ctx, info) {
  return ctx.db.mutation.deletePost(
  {
    where: { id }
  },
    info
  );
}

Run yarn start.

Then you can run the following mutation to delete a post:

mutation {
  delete(id: "__POST_ID__") {
    id
  }
}