graphql-tools 的理解与使用

本文来源：https://github.com/ardatan/graphql-tools

When using graphql-tools, you describe the schema as a GraphQL type language string：

const typeDefs = /* GraphQL */ `
  type Author {
    id: ID! # the ! means that every author object _must_ have an id
    firstName: String
    lastName: String
    """
    the list of Posts by this author
    """
    posts: [Post]
  }
  type Post {
    id: ID!
    title: String
    author: Author
    votes: Int
  }
  # the schema allows the following query:
  type Query {
    posts: [Post]
  }
  # this schema allows the following mutation:
  type Mutation {
    upvotePost(postId: ID!): Post
  }
  # we need to tell the server which types represent the root query
  # and root mutation types. We call them RootQuery and RootMutation by convention.
  schema {
    query: Query
    mutation: Mutation
  }
`
export default typeDefs

Then you define resolvers as a nested object that maps type and field names to resolver functions:

const resolvers = {
  Query: {
    posts() {
      return posts
    }
  },
  Mutation: {
    upvotePost(_, { postId }) {
      const post = find(posts, { id: postId })
      if (!post) {
        throw new Error(`Couldn't find post with id ${postId}`)
      }
      post.votes += 1
      return post
    }
  },
  Author: {
    posts(author) {
      return filter(posts, { authorId: author.id })
    }
  },
  Post: {
    author(post) {
      return find(authors, { id: post.authorId })
    }
  }
}
export default resolvers

At the end, the schema and resolvers are combined using makeExecutableSchema:

import { makeExecutableSchema } from '@graphql-tools/schema'
const executableSchema = makeExecutableSchema({
  typeDefs,
  resolvers
})