类型为"用户"的字段"我"必须有一个子字段选择

Question

嗨,我正在努力学习GraphQL语言.我有以下代码片段.

// Welcome to Launchpad!
// Log in to edit and save pads, run queries in GraphiQL on the right.
// Click "Download" above to get a zip with a standalone Node.js server.
// See docs and examples at https://github.com/apollographql/awesome-launchpad

// graphql-tools combines a schema string with resolvers.
import { makeExecutableSchema } from 'graphql-tools';

// Construct a schema, using GraphQL schema language
const typeDefs = `
    type User {
        name: String!
        age: Int!
    }

    type Query {
        me: User
    }
`;

const user = { name: 'Williams', age: 26};

// Provide resolver functions for your schema fields
const resolvers = {
  Query: {
    me: (root, args, context) => {
      return user;
    },
  },
};

// Required: Export the GraphQL.js schema object as "schema"
export const schema = makeExecutableSchema({
  typeDefs,
  resolvers,
});

// Optional: Export a function to get context from the request. It accepts two
// parameters - headers (lowercased http headers) and secrets (secrets defined
// in secrets section). It must return an object (or a promise resolving to it).
export function context(headers, secrets) {
  return {
    headers,
    secrets,
  };
};

// Optional: Export a root value to be passed during execution
// export const rootValue = {};

// Optional: Export a root function, that returns root to be passed
// during execution, accepting headers and secrets. It can return a
// promise. rootFunction takes precedence over rootValue.
// export function rootFunction(headers, secrets) {
//   return {
//     headers,
//     secrets,
//   };
// };

请求:

{
  me
}

响应:

{
  "errors": [
    {
      "message": "Field \"me\" of type \"User\" must have a selection of subfields. Did you mean \"me { ... }\"?",
      "locations": [
        {
          "line": 4,
          "column": 3
        }
      ]
    }
  ]
}

有谁知道我做错了什么？怎么解决？

Answer 1

来自文档:

GraphQL对象类型具有名称和字段,但在某些时候,这些字段必须解析为某些具体数据.这就是标量类型的来源:它们代表查询的叶子.

GraphQL要求您以仅返回具体数据的方式构造查询.每个字段必须最终解析为一个或多个标量(或枚举).这意味着您不能只请求解析为某种类型的字段,而不会指明您想要返回该类型的哪些字段.

这就是您收到的错误消息告诉您 - 您请求了一个User类型,但您没有告诉GraphQL至少有一个字段从该类型返回.

要修复它,只需将您的请求更改为包含name如下:

{
  me {
    name
  }
}

......或age.或两者.但是,您不能请求特定类型并期望GraphQL为其提供所有字段 - 您将始终必须为该类型提供选择(一个或多个)字段.