如何使用Rails include? [英] How to use Rails include?

问题描述

我有一个有很多订单的模型用户

I have a model user with many orders

 class User < ApplicationRecord 
  has_many :orders, inverse_of: :user, dependent: restrict_with_exception
end

和模型顺序如下:-

Class Order < ApplicationRecord
 belongs_to :user, inverse_of: :order
end

我想获取所有订单，但要在同一组中包含user.name和user.mobile之类的用户详细信息.在这种情况下如何使用包含?

I want to fetch all orders but with details of user like user.name and user.mobile in same set. How do I use include in this case?

推荐答案

您可以通过以下提到的查询使用包含项:

You can use includes using the below mentioned query:

@users = User.where(id: 1).includes(:orders)

然后遍历@users并获取相应的用户并订购数据.

then iterate over @users and fetch the corresponding user and order data.

此外，您还可以通过以下查询使用延迟加载:

Also, you could use lazy loading as well using the below query:

@users = User.where(id: 3).joins(:orders => [:order_data]).select("orders.*, users.first_name")

在这种情况下，您将获得单个查询中的所有数据，而不会像includes那样将rails缓存db对象存储在内存中.

In this you will be getting all the data in the single query without rails caching the db objects in memory as in the case of includes.

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