javascript - 如何在 objection.js 中为模型的所有查询自动包含 `.withGraphFetched()`

Question

我定义了以下模型:

import db from "../connection.js";
import objection from "objection";
const { Model } = objection;

Model.knex(db);

class User extends Model {
  static get tableName() {
    return "users";
  }

  static get relationMappings() {
    return {
      emails: {
        relation: Model.HasManyRelation,
        modelClass: Email,
        join: {
          from: "users.id",
          to: "emails.user_id",
        }
      }
    }
  }
}

class Email extends Model {
  static get tableName() {
    return "emails";
  }

  static get relationMappings() {
    return {
      user: {
        relation: Model.BelongsToOneRelation,
        modelClass: User,
        join: {
          from: "emails.user_id",
          to: "users.id",
        },
      },
    };
  }
}

要使用电子邮件地址查询用户，需要每次显式运行withGraphFetched()，如下所示:

const myUser = await User.query().withGraphFetched("emails").findById(1)

我一直无法弄清楚要在模型定义中写些什么才能使这成为可能，而且我在网上也没有看到任何此类示例。是否可以始终将 withGraphFetched("emails") 自动包含在查询中，这样就不必每次都明确写出来？

Answer 1

这样的东西不存在。也许您可以在 beforeFind 中创建逻辑hook 将 eager loader 添加到 knex 实例，但它可能会产生许多不希望的和奇怪的副作用。

通常的做法是为特定情况添加一个方法:

class User extends Model {
  static get tableName() {
    return "users";
  }

  static get relationMappings() {
    return {
      emails: {
        relation: Model.HasManyRelation,
        modelClass: Email,
        join: {
          from: "users.id",
          to: "emails.user_id",
        }
      }
    }
  }

  static async getUser (id) { // Or maybe getUserWithEmails
      return await this.query().withGraphFetched("emails").findById(id)
  }
}

然后你可以:

const myUser = await User.getUser(id)