node.js - 如何使用 sequelize 定义表关联。 TypeError : User. hasMany 不是函数

Question

我正在开发电子商务 Express API，并且正在使用“sequelize”模块进行数据库操作。
现在我只有两张 table :

我的项目结构如下:

bin
 -www
config
 -database.js
models
 -order.js
 -user.js
routes
 -user.js
.env
app.js
package.json
package-lock.json

database.js 文件:

    require('dotenv').config();
    const Sequelize = require('sequelize');

    module.exports = new Sequelize(
        process.env.DATABASE_NAME,
        process.env.DATABASE_USERNAME,
        process.env.DATABASE_PASSWORD, {
            port: process.env.DATABASE_PORT,
            host: process.env.DATABASE_HOST,
            dialect: 'mysql',
        }

);

User.hasMany(Order);
Order.belongsTo(User, {constraints: false});

模型-user.js

    const db = require('../config/database');
const Sequelize = require("sequelize");

const User = db.define('user', {
    username: {
        type: Sequelize.STRING(32),
        unique: true,
        primaryKey: true,
        allowNull: false
    },
    email: {
        type: Sequelize.STRING(254),
        unique: true,
        allowNull: false,
    },
    password: {
        type: Sequelize.STRING(128),
        allowNull: false,
    },
    /*name: {
        type: Sequelize.STRING
    },
    isAdmin: {
        type: Sequelize.BOOLEAN
    },*/
}, {
    freezeTableName: true,
    timestamps: false,
    underScored: true
    });

modules.exports=User;

模型-order.js

 const db = require('../config/database');
const Sequelize = require('sequelize');

const Order = db.define('order', {
        id: {
            type: Sequelize.INTEGER,
            primaryKey: true,
            autoIncrement: true,
            allowNull: false
        },
        dateTime: {
            type: Sequelize.DATE,
            allowNull: false
        },
        totalPrice: {
            type: Sequelize.INTEGER,
            allowNull: false
        }
    }, {
        freezeTableName: true,
        timestamps: false,
        underscored: true
    }
    );

module.exports=Order;

当我启动应用程序时，我得到

TypeError: User.hasMany is not a function
at Object.<anonymous> (C:\Users\danfe\Documents\GitHub\USocks_Backend\config\database.js:23:6)
at Module._compile (internal/modules/cjs/loader.js:701:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:712:10)
at Module.load (internal/modules/cjs/loader.js:600:32)
at tryModuleLoad (internal/modules/cjs/loader.js:539:12)
at Function.Module._load (internal/modules/cjs/loader.js:531:3)
at Module.require (internal/modules/cjs/loader.js:637:17)
at require (internal/modules/cjs/helpers.js:22:18)
at Object.<anonymous> (C:\Users\danfe\Documents\GitHub\USocks_Backend\models\user.js:1:74)
at Module._compile (internal/modules/cjs/loader.js:701:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:712:10)
at Module.load (internal/modules/cjs/loader.js:600:32)
at tryModuleLoad (internal/modules/cjs/loader.js:539:12)
at Function.Module._load (internal/modules/cjs/loader.js:531:3)
at Module.require (internal/modules/cjs/loader.js:637:17)
at require (internal/modules/cjs/helpers.js:22:18)
at Object.<anonymous> (C:\Users\danfe\Documents\GitHub\USocks_Backend\config\passport.js:6:14)
at Module._compile (internal/modules/cjs/loader.js:701:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:712:10)
at Module.load (internal/modules/cjs/loader.js:600:32)
at tryModuleLoad (internal/modules/cjs/loader.js:539:12)
at Function.Module._load (internal/modules/cjs/loader.js:531:3)

我做了一些谷歌搜索，它可能与循环依赖有关？但我敢肯定，我有疑问:
1. 怎么了？
2. 我是否正确定义了关联？
3. 什么是定义关联的正确方法？

Answer 1

是的，它来自循环依赖。当您调用“User.hasMany(Order)”时，用户尚未定义。当您想使用此关系时，请在放置之前调用“hasMany”和“belongTo”