如何在 apollo graphql 服务器中创建嵌套解析器

Question

鉴于以下 apollo 服务器 graphql 模式，我想将它们分解为单独的模块，因此我不希望在根 Query 模式下的作者查询......并希望将其分开。 所以我在将它添加到根查询之前添加了另一个名为 authorQueries 的层

type Author {
    id: Int,
    firstName: String,
    lastName: String
}  
type authorQueries {
    author(firstName: String, lastName: String): Author
}

type Query {
    authorQueries: authorQueries
}

schema {
    query: Query
}

我尝试了以下..您可以看到在指定作者函数之前将 authorQueries 添加为另一层。

Query: {
    authorQueries :{
        author (root, args) {
            return {}
       }
    }
}

在Graphiql中查询时，我还添加了额外的层..

{
    authorQueries {
        author(firstName: "Stephen") {
            id
        }
    }
}

我收到以下错误。

"message": "Resolve function for \\"Query.authorQueries\\" returned undefined",

Answer 1

要创建“嵌套”解析器，只需在父字段的返回类型上定义解析器。 在这种情况下，您的authorQueries字段返回类型authorQueries ，因此您可以将解析器放在那里：

{
  Query: { authorQueries: () => ({}) },
  authorQueries: {
    author(root, args) {
      return "Hello, world!";
    }
  }
}

所以从技术意义上讲，没有嵌套解析器这样的东西——每个对象类型都有一个简单的字段列表，这些字段有返回类型。 GraphQL 查询的嵌套是结果嵌套的原因。

Answer 2

我发现父字段上的返回函数返回类型导致this arg 被绑定，并破坏了解析器接口 b/c 嵌套解析器不是父作为第一个参数。

对于内联类型定义

import {
  graphql,
} from 'graphql';

import {
  makeExecutableSchema, IResolverObject
} from 'graphql-tools';

const types = `
type Query {
  person: User
}

type User {
  id: ID
  name: String,
  dog(showCollar: Boolean): Dog
}

type Dog {
  name: String
}
`;

const User: IResolverObject = {
  dog(obj, args, ctx) {
    console.log('Dog Arg 1', obj);
    return {
      name: 'doggy'
    };
  }
};

const resolvers = {
  User,
  Query: {
    person(obj) {
      console.log('Person Arg 1', obj);
      return {
        id: 'foo',
        name: 'bar',
      };
    }
  }
};

const schema = makeExecutableSchema({
  typeDefs: [types],
  resolvers
});

const query = `{ 
  person {
    name,
    dog(showCollar: true) {
      name
    }
  }
 }`;


graphql(schema, query).then(result => {
  console.log(JSON.stringify(result, null, 2));
});

// Person Arg 1 undefined
// Dog Arg 1 { id: 'foo', name: 'bar' }
// {
//   "data": {
//     "person": {
//       "name": "bar",
//       "dog": {
//         "name": "doggy"
//       }
//     }
//   }
// }

您还可以使用addResolveFunctionsToSchema如下面的要点所示。

https://gist.github.com/blugavere/4060f4bf2f3d5b741c639977821a254f

Answer 3

Apollo 官方相关文档（里面有很好的例子）：

解析器链

https://www.apollographql.com/docs/apollo-server/data/resolvers/#resolver-chains

 /* code from: https://www.apollographql.com/docs/apollo-server/data/resolvers/#resolver-chains */ const { ApolloServer, gql } = require('apollo-server'); const libraries = [ { branch: 'downtown' }, { branch: 'riverside' }, ]; // The branch field of a book indicates which library has it in stock const books = [ { title: 'The Awakening', author: 'Kate Chopin', branch: 'riverside' }, { title: 'City of Glass', author: 'Paul Auster', branch: 'downtown' }, ]; // Schema definition const typeDefs = gql` # A library has a branch and books type Library { branch: String! books: [Book!] } # A book has a title and author type Book { title: String! author: Author! } # An author has a name type Author { name: String! } # Queries can fetch a list of libraries type Query { libraries: [Library] } `; // Resolver map const resolvers = { Query: { libraries() { // Return our hardcoded array of libraries return libraries; } }, Library: { books(parent) { // Filter the hardcoded array of books to only include // books that are located at the correct branch return books.filter(book => book.branch === parent.branch); } }, Book: { // The parent resolver (Library.books) returns an object with the // author's name in the "author" field. Return a JSON object containing // the name, because this field expects an object. author(parent) { return { name: parent.author }; } } // Because Book.author returns an object with a "name" field, // Apollo Server's default resolver for Author.name will work. // We don't need to define one. }; // Pass schema definition and resolvers to the // ApolloServer constructor const server = new ApolloServer({ typeDefs, resolvers }); // Launch the server server.listen().then(({ url }) => { console.log(`🚀 Server ready at ${url}`); });