GraphQL 错误：预期的 GraphQL 命名类型，但得到：{}答案

【问题标题】：GraphQL error: Expected GraphQL named type but got: {}GraphQL 错误：预期的 GraphQL 命名类型，但得到：{}
【发布时间】：2019-08-14 08:25:32
【问题描述】：

我有 2 个自定义 graphql 类型，entityType 和 containerType，其中 1 个容器可以有多个实体。

所以，我通过以下代码将所有实体与它们各自的容器绑定：

const graphql = require('graphql')
const _ = require('lodash')

const UserType = require('./userSchema')
const ContainerType = require('./containerSchema')

const Container = require('../models/container')
const Entity = require('../models/entity')
const {
    GraphQLObjectType, 
    GraphQLString,
    GraphQLBoolean,
    GraphQLSchema,
    GraphQLInt,
    GraphQLID,
    GraphQLList,
    GraphQLNonNull,
    GraphQLUnionType
} = graphql

const EntityType = new GraphQLObjectType({
    name: "Entity",
    fields: () => ({
        name: { type: new GraphQLNonNull(GraphQLString) },
        container: { 
            type: ContainerType,
            resolve: function(parent, args) {
                return Container.findById(parent.containerId)
            } 
        },
        type: { type: new GraphQLNonNull(GraphQLString) },
        detail: { type: new GraphQLNonNull(GraphQLString) },
        start: { type: GraphQLString },
        end: { type: GraphQLString }
    })
})
module.exports = { EntityType }

我很确定 containerType 正在工作，因为我正在使用它，它正在其他地方使用并且运行良好。下面是容器类型的代码：

const graphql = require('graphql')
const _ = require('lodash')

const UserType = require('./userSchema')
const { EntityType } = require('./entitySchema')

const User = require('../models/user')
const Container = require('../models/container')
const Entity = require('../models/entity')

const { 
    GraphQLObjectType, 
    GraphQLString,
    GraphQLBoolean,
    GraphQLSchema,
    GraphQLInt,
    GraphQLID,
    GraphQLList,
    GraphQLNonNull
} = graphql

const ContainerType = new GraphQLObjectType ({
    name: 'Container',
    fields: () => ({
        id: { type: GraphQLID },
        name: { type: GraphQLString },
        user: { 
            type: UserType,
            resolve: function (parent, args) {
                return User.findById(parent.userId)
            }
        },
        parent: {
            type: ContainerType,
            resolve: function (parent, args) {
                return Container.findById(parent.parentContainer)
            }
        },
        detail: { type: GraphQLString },
        start: { type: GraphQLString },
        end: { type: GraphQLString },
        createdAt: { type: GraphQLString },
        category: { type: GraphQLString },
        status: { type: GraphQLString },
        entities: {
            type: GraphQLList(EntityType),
            resolve: async function(parent, args) {
                return await Entity.find({ containerId: parent.id })
            }
        }
    })
})



module.exports = ContainerType

终端上没有显示错误，但 Graphiql 控制台在加载时显示以下错误：

{
  "errors": [
    {
      "message": "The type of Entity.container must be Output Type but got: {}."
    },
    {
      "message": "Expected GraphQL named type but got: {}."
    }
  ]
}

【问题讨论】：

标签： graphql

【解决方案1】：

我发现问题出在所谓的“模块周期”上。 this post 对解决它很有帮助。

最后，我最终在一个文件中添加了 EntitySchema 和 ContainerSchema，代码如下：

const graphql = require('graphql')
const _ = require('lodash')

const UserType = require('./userSchema')

const User = require('../models/user')
const Container = require('../models/container')
const Entity = require('../models/entity')

const { 
    GraphQLObjectType, 
    GraphQLString,
    GraphQLBoolean,
    GraphQLInt,
    GraphQLID,
    GraphQLList,
    GraphQLNonNull
} = graphql

const EntityType = new GraphQLObjectType ({
    name: "Entity",
    fields: () => ({
        name: { type: new GraphQLNonNull(GraphQLString) },
        container: { 
            type: ContainerType,
            resolve: (parent, args) => {
                return Container.findById(parent.containerId)
            }
        },
        type: { type: new GraphQLNonNull(GraphQLString) },
        detail: { type: new GraphQLNonNull(GraphQLString) },
        start: { type: GraphQLString },
        end: { type: GraphQLString }
    })
})

const ContainerType = new GraphQLObjectType ({
    name: 'Container',
    fields: () => ({
        id: { type: GraphQLID },
        name: { type: GraphQLString },
        user: { 
            type: UserType,
            resolve: function (parent, args) {
                return User.findById(parent.userId)
            }
        },
        parent: {
            type: ContainerType,
            resolve: function (parent, args) {
                return Container.findById(parent.parentContainer)
            }
        },
        detail: { type: GraphQLString },
        start: { type: GraphQLString },
        end: { type: GraphQLString },
        createdAt: { type: GraphQLString },
        category: { type: GraphQLString },
        status: { type: GraphQLString },
        entities: {
            type: GraphQLList(EntityType),
            resolve: async function(parent, args) {
                return await Entity.find({ containerId: parent.id })
            }
        }
    })
})

module.exports = {
    EntityType, 
    ContainerType
}

【讨论】：