循环依赖不能拆分到各自的文件中

Question

有两个对象，Users和Company，每个用户为一个Company工作，从而有一个companyId，通过GraphQL引用。同样，每个公司都有一个为他们工作的用户列表。

代码如下：

company.js

const UserType = require('./user')

const CompanyType = new GraphQLObjectType({
  name: 'Company',
  fields: () => ({
    id: { type: GraphQLString },
    name: { type: GraphQLString },
    users: {
      type: new GraphQLList(UserType),        --------> Error:Expected {} to be a GraphQL type.
                                                        Expected UserType to be a GraphQL type.
      async resolve(parentValue, args) {
        return await axios(
          `http://localhost:3001/company/${parentValue.id}/users`
        ).then(({ data }) => data)
      },
    },
  }),
})

user.js

const CompanyType = require('./company')

const UserType = new GraphQLObjectType({
  name: 'User',
  fields: () => ({
    id: { type: GraphQLString },
    age: { type: GraphQLInt },
    name: { type: GraphQLString },
    company: {
      type: CompanyType,
      async resolve(parentValue, args) {
        console.log(parentValue)
        return await axios(
          `http://www.localhost:3001/company/${parentValue.companyId}`
        ).then((response) => response.data)
      },
    },
  }),
})

rootquery.js

const UserType = require('./user')
const CompanyType = require('./company')

const RootQuery = new GraphQLObjectType({
  name: 'RootQueryObjectType',
  fields: {
    user: {
      type: UserType,
      args: {
        id: { type: GraphQLString },
      },
      resolve: async (parentValue, args) => {
        return await axios(`http://localhost:3001/users/${args.id}`).then(
          ({ data }) => data
        )
      },
    },
    company: {
      type: CompanyType,
      args: {
        id: { type: GraphQLString },
      },
      resolve: async (parentValue, args) => {
        return await axios(`http://localhost:3001/company/${args.id}`).then(
          ({ data }) => data
        )
      },
    },
  },
})

由于循环依赖性，该错误是可以理解的。如果我将 user.js 和 company.js 的代码放入 rootquery.js，则不会出现错误。有没有办法将这些文件分开，而不运行变成空对象错误？

Answer 1

经过相当多的研究后，发现无论何时需要使用循环依赖，都必须在代码中的那个位置要求它，而不是要求它作为变量。例如

之前：

const UserType = require('./user')        ---> This was null/empty as it wasn't yet 
                                               created

const CompanyType = new GraphQLObjectType({
  name: 'Company',
  fields: () => ({
    id: { type: GraphQLString },
    name: { type: GraphQLString },
    users: {
      type: new GraphQLList(UserType),        --------> Error:Expected {} to be a 
                                                              GraphQL type.
                                                        Expected UserType to be a 
                                                              GraphQL type.
      async resolve(parentValue, args) {
        return await axios(
          `http://localhost:3001/company/${parentValue.id}/users`
        ).then(({ data }) => data)
      },
    },
  }),
})

为了解决这个问题，我在需要的地方精确地需要了必要的模块

解法：

const UserType = new GraphQLObjectType({
  name: 'User',
  fields: () => ({
    name: { type: GraphQLString },
    id: { type: GraphQLString },
    age: { type: GraphQLInt },
    company: {
      **type: require('./company'),**            -----> This is where a dynamic 
                                                                 import                                                               
                                                             is being made
      async resolve(parentValue, args) {
        return await axios(
          `http://localhost:3001/users/${parentValue.id}`
        ).then(({ data }) => data)
      },
    },
  }),
})

循环依赖不能拆分到各自的文件中

Circular Dependencies cannot be split into their respective files

javascript

node.js

graphql