适用于多种型号的范围

问题描述

我有几个对象都有一个 approved 字段.

I have several objects that all have an approved field.

实现跨所有模型使用的范围的最佳方法是什么?

What would be the best way to implement a scope to use across all models?

例如，我有一个 sighting 对象和一个 comment 对象.它们都必须经过管理员的批准才能向公众开放.

For example, I have a sighting object and a comment object. They both have to be approved by an admin before being availalbe to the public.

那么如何创建一个范围，分别返回 comment.approved 和 sighting.approved 而不在每个模型上重复它?这是担忧的地方吗?

So how can I create a scope that returns comment.approved as well as sighting.approved respectively without repeating it on each model? Is this where concerns comes into play?

推荐答案

虽然如果您只想要范围功能，只需在每个模型中声明一个范围就可以了.如果您认为这会发生，使用 ActiveSupport::Concern 还可以让您添加其他方法.举个例子:

While just declaring a scope in each model is fine if you just want the scoping functionality. Using an ActiveSupport::Concern will give you the ability to add additional methods as well if that's something you think is going to happen. Here's an example:

# /app/models/concerns/approved.rb
module Approved
  extend ActiveSupport::Concern

  included do
    default_scope { where(approved: false) }
    scope :approved, -> { where(approved: true) }
  end

  def unapprove
    update_attribute :approved, false
  end
end

class Sighting < ActiveRecord::Base
  include Approved
end

class Comment < ActiveRecord::Base
  include Approved
end

然后您可以进行诸如Sighting.approved 和Comment.approved 之类的调用，以获取相应的已批准记录列表.您还可以使用 unapprove 方法，并且可以执行诸如 Comment.approved.first.unapprove 之类的操作.

Then you can make calls like Sighting.approved and Comment.approved to get the appropriate list of approved records. You also get the unapprove method and can do something like Comment.approved.first.unapprove.

在这个例子中，我还包括了 default_scope 这意味着像 Sighting.all 或 Comment.all 这样的调用将只返回未经批准的物品.我只是将其作为示例包含在内，它可能不适用于您的实现.

In this example, I've also included default_scope which will mean that calls like Sighting.all or Comment.all will return only unapproved items. I included this just as an example, it may not be applicable to your implementation.

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