Sequelize调用findAll/create报错：函数不存在或无法读取属性

我是Sequelize新手，查询模型调用API时出现findAll is not a function错误，用POST调用create()也碰到同类问题。改了模型导入导出方式没解决；修改模型文件后，又出现Cannot read properties of undefined (reading 'findAll')错误。

相关代码文件 #

route.ts文件 #

import { create_brands, fetch_brands } from "../../../service/dbService";

export const POST = async (req: Request, res: Response) => {
  try {
    const created_brands = await create_brands(req.body);
    return new Response(JSON.stringify(created_brands));
  } catch (err) {
    return new Response(`Error posting data: ${err.message}`, {
      status: 500,
    });
  }
};

export const GET = async (req: Request, res: Response) => {
  try {
    const all_brands = await fetch_brands();
    return new Response(JSON.stringify(all_brands));
  } catch (err) {
    return new Response(`Error fetching data: ${err.message}`, {
      status: 500,
    });
  }
};

dbService.js文件 #

import { brands } from "../database/models";

console.log(JSON.stringify(brands));

export async function create_brands({ name }) {
  const createdBrand = await brands.create({
    name: name,
  });
  return createdBrand.dataValues;
}

export async function fetch_brands() {
  const allBrands = await brands.findAll();
  return allBrands;
}

初始models/brand.js文件 #

const { Model, DataTypes } = require("sequelize");
import connection from "../connection";

class brands extends Model {
  static associate(models) {
    brands.hasMany(models.products, {
      sourceKey: "id",
      foreignKey: "brandId",
      as: "products",
    });
  }
}

brands.init(
  {
    id: {
      allowNull: false,
      primaryKey: true,
      type: DataTypes.UUID,
      defaultValue: DataTypes.UUIDV4,
    },
    name: DataTypes.STRING,
  },
  {
    sequelize: connection,
    modelName: "brands",
    timestamps: true,
    underscored: true,
  }
);

export default brands;

models/index.js文件 #

const sequelize = require("../connection");
const brands = require("./brands");
const products = require("./products");

export { sequelize, brands, products };

connection.js文件 #

const { Sequelize } = require("sequelize");

const sequelize = new Sequelize({
  dialect: "mysql",
  dialectModule: require("mysql2"),
  host: process.env.DB_HOST,
  username: process.env.DB_USER,
  password: process.env.DB_PASS,
  database: process.env.DB_NAME,
});

async function testConnection() {
  try {
    await sequelize.authenticate();
    console.log("Connection has been established successfully.");
  } catch (error) {
    console.error("Unable to connect to the database:", error);
  }
}

testConnection();

module.exports = sequelize;

修改后的brands.js文件 #

const { Model } = require("sequelize");
module.exports = (sequelize, DataTypes) => {
class brands extends Model {
    static associate(models) {
    this.hasMany(models.products);
  }
}

brands.init(
  {
    id: {
      allowNull: false,
      primaryKey: true,
      type: DataTypes.UUID,
      defaultValue: DataTypes.UUIDV4,
    },
    name: DataTypes.STRING,
  },
  {
    sequelize: connection,
    modelName: "brands",
    timestamps: true,
    underscored: true,
  }
);

return brands;
};

修改后的products.js文件 #

const { Model } = require("sequelize");

module.exports = (sequelize, DataTypes) => {
  class products extends Model {
    static associate(models) {
      this.belongsTo(models.brands);
    }
  }
  products.init(
    {
      id: {
        allowNull: false,
        primaryKey: true,
        type: DataTypes.UUID,
        defaultValue: DataTypes.UUIDV4,
      },
      name: {
        type: DataTypes.STRING,
      },
      images: {
        type: DataTypes.STRING,
      },
      brandId: {
        type: DataTypes.UUID,
        field: "brand_id",
        references: {
          model: brands,
          key: "id",
        },
      },
    },
    {
      sequelize: connection,
      modelName: "products",
      timestamps: true,
      underscored: true,
    }
  );

  return products;
};

问题根源与解决步骤 #

1. 核心问题：模型未正确初始化 #

修改后的模型改成了工厂函数（接收sequelize和DataTypes的函数），但models/index.js直接导出了未执行的工厂函数，导致brands是函数而非Sequelize模型实例，自然调用不了findAll/create方法；后续又因引用未定义变量导致模型变成undefined。

2. 修正models/index.js的模型初始化逻辑 #

const sequelize = require("../connection");
const DataTypes = require("sequelize").DataTypes;

// 导入模型工厂函数
const brandsFactory = require("./brands");
const productsFactory = require("./products");

// 执行工厂函数，生成模型实例
const brands = brandsFactory(sequelize, DataTypes);
const products = productsFactory(sequelize, DataTypes);

// 建立模型关联
brands.associate({ products });
products.associate({ brands });

module.exports = { sequelize, brands, products };

3. 修复模型文件中的变量引用错误 #

修改后的模型里误用了未定义的connection，要替换成传入的sequelize参数：

修正后的brands.js

const { Model } = require("sequelize");
module.exports = (sequelize, DataTypes) => {
class brands extends Model {
    static associate(models) {
    this.hasMany(models.products, {
      sourceKey: "id",
      foreignKey: "brandId",
      as: "products",
    });
  }
}

brands.init(
  {
    id: {
      allowNull: false,
      primaryKey: true,
      type: DataTypes.UUID,
      defaultValue: DataTypes.UUIDV4,
    },
    name: DataTypes.STRING,
  },
  {
    sequelize: sequelize,
    modelName: "brands",
    timestamps: true,
    underscored: true,
  }
);

return brands;
};

修正后的products.js

const { Model } = require("sequelize");

module.exports = (sequelize, DataTypes) => {
  class products extends Model {
    static associate(models) {
      this.belongsTo(models.brands, {
        foreignKey: "brandId",
        targetKey: "id",
      });
    }
  }
  products.init(
    {
      id: {
        allowNull: false,
        primaryKey: true,
        type: DataTypes.UUID,
        defaultValue: DataTypes.UUIDV4,
      },
      name: {
        type: DataTypes.STRING,
      },
      images: {
        type: DataTypes.STRING,
      },
      brandId: {
        type: DataTypes.UUID,
        field: "brand_id",
        references: {
          model: "brands",
          key: "id",
        },
      },
    },
    {
      sequelize: sequelize,
      modelName: "products",
      timestamps: true,
      underscored: true,
    }
  );

  return products;
};

4. 统一模块规范 #

项目中混用了ES模块（import/export）和CommonJS（require/module.exports），建议统一规范：

• 如果用Node.js环境，在package.json中添加"type": "module"，全量改用ES模块语法；
• 或者将dbService.js改为CommonJS：

const { brands } = require("../database/models");

console.log(JSON.stringify(brands));

async function create_brands({ name }) {
  const createdBrand = await brands.create({
    name: name,
  });
  return createdBrand.dataValues;
}

async function fetch_brands() {
  const allBrands = await brands.findAll();
  return allBrands;
}

module.exports = { create_brands, fetch_brands };

5. 验证结果 #

启动项目后，查看dbService.js中打印的brands，如果输出包含findAll、create等方法，说明模型初始化成功，API调用即可正常工作。

内容的提问来源于stack exchange，提问作者Lavalse67