has_many 和 No method 错误问题 [英] has_many and No method error issue

问题描述

我有两个表:Stores 和 products.商店模型有一个 has_many :products 并且产品有一个 belongs_to :store

I have two tables: Stores and products. The store model has a has_many :products and the products has a belongs_to :store

我正在尝试在 rails 控制台中执行此操作:

I'm trying to do this though in the rails console:

Store.where(open: true).products.where("created_at <= ?", 1.month.ago)

并得到错误(稍微解释一下):NoMethodError: undefined method products for #<Store

and get the error (paraphrased a bit): NoMethodError: undefined method products for #<Store

推荐答案

不是一件很容易的事情 - products 是在 Store 的实例上定义的方法，并且你在关系上调用它.我可能会去:

Not a very easy thing to do - products is a method defined on an instance of Store and you are calling it on the relation. I would probably go with:

Product.where(store_id: Store.where(open:true).pluck(:id)).where("created_at <= ?", 1.month.ago)

这将生成两个 db 调用，但也会返回一个干净且易于查询的范围.另一种方法是使用 join:

which would generate two db calls, but also returns a clean and easy to query scope. Another approach would be to use join:

Product.joins(:store).where(store: { open: true }).where("created_at <= ?", 1.month.ago)

这将完成一个查询的工作，但由于连接，操作结果范围不会那么容易.

This will do the work with one query, but due to the join it won't be that easy to manipulate the resulting scope that easily.

这篇关于has_many 和 No method 错误问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！