NodeJs 中的 GraphQl - 对象类型的解析器

Posted 2023-03-08

【中文标题】NodeJs 中的 GraphQl - 对象类型的解析器

【英文标题】：GraphQl in NodeJs - Resolver for Object Types

【发布时间】：2020-03-17 12:07:18

【问题描述】：

我刚刚开始在 NodeJs 中使用 GraphQl。我了解类型的解析器在下面的示例中编码。

但我无法弄清楚解析器用于关系类型的位置。例如，下面的 Type Book 有一个属性 author ，如果被查询，它应该返回 Author 类型。我在哪里放置解析器来解析本书的作者？

// Construct a schema, using GraphQL schema language
var schema = buildSchema(`  
  type Book 
      id: ID!
      name: String!
      genre: String!
      author: Author
  
  type Author 
      id: ID!
      name: String!
      age: String!
  

  type Query 
      books: [Book]
      authors: [Author]
      book(id: ID): Book
      author(id: ID): Author
  
`);

const root = 
    books: () => 
        return Book.find();
    ,
    authors: () => 
        return Author.find();
    ,
    book:(id) => 
        return Book.findById(id);
    ,
    author:(id) => 
        return Author.findById(id);
    


const app = express()
app.listen(5000, () =>
   console.log('listening for request');
)

app.use('/graphql', graphqlHTTP(
    schema: schema,
    rootValue: root,
    graphiql: true
))

【问题讨论】：

我相信是的。我在将 graphqlHTTP 设置为 express 的中间件时使用这个 rootValue: root。我正在扩展这些示例graphql.org/graphql-js/running-an-express-graphql-server

目前官方文档非常缺乏。你真的shouldn't be using buildSchema in the first place。

@DanielRearden 真棒。你给了我我想要的东西。这解决了我的很多问题。谢谢

【参考方案1】：

您需要为 Book 类型定义特定的解析器。我建议从graphql-tools 中获取makeExecutableSchema，这样您就可以轻松构建所需的关系解析器。我已复制并更改了您的解决方案以达到预期的结果。

const graphqlHTTP = require("express-graphql")
const express = require("express");
const  makeExecutableSchema  = require("graphql-tools")

const typeDefs = `  
  type Book 
      id: ID!
      name: String!
      genre: String!
      author: Author
  
  type Author 
      id: ID!
      name: String!
      age: String!
  

  type Query 
      books: [Book]
      authors: [Author]
      book(id: ID): Book
      author(id: ID): Author
  
`;

const resolvers = 
    Book: 
        author: (rootValue, args) => 
            // rootValue is a resolved Book type.

            return 
                id: "id",
                name: "dan",
                age: "20"
            
        
    ,
    Query: 
        books: (rootValue, args) => 
            return [ id: "id", name: "name", genre: "shshjs" ];
        ,
        authors: (rootValue, args) => 
            return Author.find();
        ,
        book: (rootValue,  id ) => 
            return Book.findById(id);
        ,
        author: (rootValue,  id ) => 
            return Author.findById(id);
        
    


const app = express();

app.listen(5000, () => 
    console.log('listening for request');
)

app.use('/graphql', graphqlHTTP(
    schema: makeExecutableSchema( typeDefs, resolvers ),
    graphiql: true
))