mysql - 在两个模型上使用 hasMany 处理 Sequelize Eager Load Error

Question

我有两个模型(类(class)和公司)，它们作为外键关联到日志记录模型中。我可以在日志模型的查询中包含/加入类(class)模型，而不会出现问题，但是公司模型总是抛出 Sequelize 急切加载错误。

我尝试在 hasMany 和 BelongsTo 关联上使用“as:company”，但这没有用。我也尝试过重新排序，但没有成功。

// The log model

module.exports = (sequelize, DataTypes) => {
  const Log = sequelize.define("Log", {
    user: {
      type: DataTypes.STRING,
      allowNull: false
    },
    {...other values}
  })

  Log.associate = models => {
    models.Log.belongsTo(models.Company, {
      foreignKey: {
        allowNull: false
      }
    })
  }

  Log.associate = models => {
    models.Log.belongsTo(models.Course, {
      foreignKey: {
        allowNull: false
      }
    })
  }

  return Log
}


// the Course model

module.exports = (sequelize, DataTypes) => {
  const Course = sequelize.define("Course", {
    name: {
      type: DataTypes.STRING,
      allowNull: false
    },
    courseId: {
      type: DataTypes.INTEGER
    }
  })

  Course.associate = models => {
    models.Course.hasMany(models.Log)
  }

  return Course
}

// The Company model which does not work in a query:

module.exports = (sequelize, DataTypes) => {
  const Company = sequelize.define("Company", {
    name: {
      type: DataTypes.STRING,
      allowNull: false
    }
  })

  Company.associate = models => {
    models.Company.hasMany(models.Log)
  }

  return Company
}

// And finally the query, where swapping the include to be [db.Course] works, however db.Company does not:

db.Log.findAll({
  attributes: [
    "CompanyId",
  ],
  include: [db.Company]
})
.then(dbCompanies => {
  res.json(dbCompanies)
})
.catch(err => res.send(err));```

Including the course model brings in that data without any issue, but any time the company is used, it throws an error. They are identical, from what I can see.

Answer 1

你的逻辑是正确的，但语法错误。加载模型时会调用模型的“关联”方法。您希望将“Log”模型与“Company”和“Course”模型关联起来，但您定义了“associate”两次，并且与 JavaScript 中的所有变量一样，只有最后一个定义很重要。您的原始定义(关联“Log”和“Company”模型)已被覆盖，这就是您收到上述错误的原因。

相反，您可以创建一个“关联”方法来创建这两种关联:

Log.associate = models => {
  models.Log.belongsTo(models.Company, {
    foreignKey: {
      allowNull: false
    }
  })

  models.Log.belongsTo(models.Course, {
    foreignKey: {
      allowNull: false
    }
  })
}