如何在 apollo graphql 服务器中创建嵌套解析器

Question

给定以下 apollo 服务器 graphql 架构 我想将它们分解为单独的模块，因此我不希望在根查询模式下进行作者查询..并希望将其分开。所以我在将其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添加了 authorQueries 作为另一层。

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

在 Graphiql 中查询时，我还添加了那个额外的层..

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

我收到以下错误。

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

Answer 1

Apollo Official 相关文档（Great 内有示例）：

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}`);
});

Answer 2

我发现在父字段返回类型上返回函数会导致 this arg 被绑定，并破坏解析器接口 b/c 嵌套解析器不会将父级作为第一个参数。

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"
//       }
//     }
//   }
// }

您也可以使用addResolveFunctionsToSchema，如下所示。

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

Answer 3

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!";
    }
  }
}

因此，从技术意义上讲，不存在嵌套解析器之类的东西 - 每个对象类型都有一个平面的字段列表，并且这些字段具有返回类型。 GraphQL 查询的嵌套是结果嵌套的原因。