ruby-on-rails - "one, other or both"案例的更好解决方案

Question

我正在检查一些代码，并且出现了类似于以下内容的内容:

def between_dates(date_1, date_2)
  if date_1 && date_2
    conditions "created_at >= date_1 AND created_at <= date_2"
  elseif date_1
    conditions "created_at >= date_1"
  elseif date_2
    conditions "created_at <= date_2"
  end
end

它看起来是一种可以改进的代码，但我找不到更优雅的解决方案来处理这种琐碎而常见的条件语句。

当我们必须为一个、另一个或两者返回一个值时，我正在为这个问题寻找更好的答案。

Answer 1

Rails 允许您动态构建查询。这是一个使用 scopes 的示例和一个类方法。由于范围总是返回一个 ActiveRecord::Relation 对象(即使该 block 返回 nil)，它们是可链接的:

class Event < ApplicationRecord
  scope :created_before, -> (date) { where('created_at <= ?', date) if date }
  scope :created_after,  -> (date) { where('created_at >= ?', date) if date }

  def self.created_between(date_1, date_2)
    created_after(date_1).created_before(date_2)
  end
end

示例用法:

Event.created_between(nil, Date.today)
# SELECT `events`.* FROM `events` WHERE (created_at <= '2018-05-15')

Event.created_between(Date.yesterday, nil)
# SELECT `events`.* FROM `events` WHERE (created_at >= '2018-05-14')

Event.created_between(Date.yesterday, Date.today)
# SELECT `events`.* FROM `events` WHERE (created_at >= '2018-05-14') AND (created_at <= '2018-05-15')