出现这个错误通常是因为没有在Model中定义需要查询的字段。解决方法是定义需要查询的字段,例如在mongoose中,可以使用findById而不是findOneById。以下是一个示例代码:
const { ApolloServer } = require('apollo-server-express');
const mongoose = require('mongoose');
// 定义schema
const typeDefs = `
  type User {
    id: ID!
    name: String!
    email: String!
  }
  type Query {
    user(id: ID!): User
  }
`;
// 定义resolvers
const resolvers = {
  Query: {
    user: async (parent, args) => {
      const { id } = args;
      const User = mongoose.model('User');
      const user = await User.findById(id);
      return user;
    }
  }
};
// 创建服务器
const server = new ApolloServer({ typeDefs, resolvers });