MainQuery类型必须定义一个或多个字段。 Express GraphQL MongoDB

Question

我是不熟悉graphQL的MERN的人。我收到以下错误。我被困了两天。我编写了MainSchema和GraphQL查询。我不太了解我对哪里出错了。

以下是后端代码，其中我使用Express，GraphQL，MongoDB。请让我知道是否遗漏了任何东西

grapqiQL

                    {
                        "errors": [
                            {
                            "message": "Type MainQuery must define one or more fields."
                            },
                            {
                            "message": "Type Mains must define one or more fields."
                            }
                        ]
                    } 

MainSchema：MongoDB模式

                    let Mongoose=require('mongoose');

                let MainSchema=new Mongoose.Schema({
                    id:String,
                    MainName:{type:String,required:true,unique:true},
                    Owner:String,
                    MainType:String,
                    subCategory1:{
                        subCategory1Name:String,
                        CreatedDate:{type:Date,default:Date}
                    },
                    subCategory2:{
                        subCategory2Id:String,
                        subCategory2Name:String,
                        subCategory2Role:Number,
                        CreatedDate:{type:Date,default:Date}
                    },                      
                    CreatedDate:{type:Date,default:Date}
                });

                module.exports=Mongoose.model('MainSchema',MainSchema);

MainType：GraphQL类型

                let GraphQLObjectType = require('graphql').GraphQLObjectType;
                let GraphQLString = require('graphql').GraphQLString;
                let GraphQLBoolean = require('graphql').GraphQLBoolean;
                let GraphQLInt = require('graphql').GraphQLInt;
                let GraphQLDate = require('graphql-date');



                let MainType = new GraphQLObjectType({
                    name:'Mains',
                    feilds:function(){
                        return{
                            id:{
                                type:GraphQLString
                            },
                            MainName:{
                                type:GraphQLString
                            },
                            Owner:{
                                type:GraphQLString
                            },
                            MainType:{
                                type:GraphQLString
                            },
                            subCategory1:{
                                subCategory1Name: {
                                                    type:GraphQLString
                                                },
                                CreatedDate:{
                                                type:GraphQLDate
                                            }
                            },          
                            subCategory2:{
                                subCategory2Id:{
                                                    type:GraphQLInt
                                            },
                                subCategory2Name:{
                                                    type:GraphQLString
                                                },
                                subCategory2Role:{
                                                    type:GraphQLInt
                                                },
                                CreatedDate:{
                                                type:GraphQLDate
                                            }          
                            },
                            CreatedDate:{
                                            type:GraphQLDate
                                        }
                        }
                    }
                });

                module.exports=MainType;

MainQueryType：graphQl查询类型

                let GraphQLObjectType = require('graphql').GraphQLObjectType;
                let GraphQLString = require('graphql').GraphQLString;
                let GraphQLList = require('graphql').GraphQLList;
                let MainSchema=require('./MainsSchema');
                let MainType=require('./MainsType');


                let QueryType=new GraphQLObjectType({
                    name:"MainQuery",
                    feilds:function(){
                        return{
                            Mains:{//List of all Mains
                                type:new GraphQLList(MainType),
                                resolve:function(){
                                    const Mains=MainSchema.find().exec()
                                    if(!Mains){
                                        throw new Error("Error")
                                    }
                                    return Mains
                                }
                            },
                        Main:{//search name
                                type:MainType,
                                args:{
                                    id:{
                                        name:'id',
                                        type:GraphQLString
                                    },
                                    MainName:{
                                        name:'MainName',
                                        type:GraphQLString
                                    }
                                },
                                resolve:function(root,params){
                                    const MainDetails=''
                                    if(params.id){
                                        MainDetails=MainSchema.find({}).exec()
                                    }else{
                                        MainDetails=MainSchema.find({MainName:params.MainName}).exec()
                                    }
                                    if(!MainDetails){
                                        throw new Error('Error')
                                    }
                                    return MainDetails
                                }
                            }
                        }
                    }
                });

                module.exports=QueryType;

MainMutation：GraphQL突变

                        let GraphQLSchema = require('graphql').GraphQLSchema;
                        let GraphQLObjectType = require('graphql').GraphQLObjectType;
                        let GraphQLString = require('graphql').GraphQLString;
                        let GraphQLNonNull = require('graphql').GraphQLNonNull;
                        let MainSchema=require('./MainsSchema');
                        let MainType=require('./MainsType');
                        let MainQueryType=require('./MainsQueryType');


                        let Mutation=new GraphQLObjectType({
                            name:"Mutation",
                            fields:function(){
                                return{
                                    addMain:{
                                        type:MainType,
                                        args:{
                                            MainName:{
                                                type:new GraphQLNonNull(GraphQLString)
                                            }
                                        },
                                        resolve:function(root,params){
                                            const MainSchema=new MainSchema(params);
                                            const newMain=MainSchema.save();
                                            if(!newMain){
                                                throw new Error("Error")
                                            }
                                            return newMain
                                        }

                                    },
                                    removeMain:{
                                        type:MainType,
                                        args:{
                                            id:{
                                                type:new GraphQLNonNull(GraphQLString)
                                            }
                                        },
                                        resolve:function(root,params){
                                            const removeMain=MainSchema.findByIdAndRemove(params.id).exec();
                                            if(!removeMain){
                                                throw new Error("Error")
                                            }
                                            return removeMain
                                        }   
                                    }
                                }
                            }
                        });

                        module.exports=new GraphQLSchema({query:MainQueryType,mutation:Mutation}); 

app.js

                    const MainSchema=require("./Mains/MainMutations");

                    app.use('/graphql',cors(),ExpressGraphQLHTTP({
                            schema:MainSchema,
                            rootValue:global,
                            graphiql:true
                    }))  

我想Type，QueryType和Mutation出了点问题，我不知道我要去哪里，我用谷歌搜索了一下，但没有发现太多有关该错误的内容，我发现那条代码不起作用我我不太了解。

任何人都可以让我知道我要去哪里了。我们会尽力帮助您。

任何人都可以指导。