根據子女的具體屬性訂購ActiveRecord實例

Question

我有兩個ActiveRecord型號 - Residence和Apartment。

class Residence < ActiveRecord::Base 
    has_many :apartments 
end 

class Apartment < ActiveRecord::Base 
    belongs_to :residence 
end 

apartments表具有字段price_from（單價）和area。所以總價的公寓是price_from * area

我也定義一個實例方法用於住宅

def min_price_for_apartment 
    apartments.minimum("price_from*area") 
end 

我能夠住宅升序/與調用此範圍降序排序。

#scope: with_children, -> { where(published: true).includes(:apartments).joins(:apartments) } 

scope: sort_by_unit_price_asc, -> { with_children.order('apartments.price_from') } 
# scope: sort_by_unit_price_asc, ->{adding desc to the end of previous scope} 

我應該怎麼做，以最低公寓價格對住宅進行分類？

UPDATE：我已經找到了用純SQL的解決方案，現在需要翻譯爲AR

# select residences.name from residences inner join apartments on residences.id = apartments.residence_id group by (residences.id) order by min(apartments.price_from*apartments.area) 

    name  
----------- 
Lorem 
Ipsum 
Quod 
Maritimus 
Amet 
(5 rows) 

附：我知道其他相關的問題和答案，但他們都沒有幫助我。我也意識到要實施基於前端的解決方案，並將這些值傳遞給data-attributes並根據它們進行排序。

Answer 1

這解決了我的問題。只需加入以備將來參考，如果有人需要。

scope :with_children, -> { where(published: true).joins(:apartments).group('residences.id') } 

    scope :sort_by_price_sqm_asc, -> { with_children.order("MIN(apartments.price_from)") } 

Answer 2

scope: sort_by_unit_price_asc, lambda {     
    with_children.group('residences.id').order('MIN(apartments.price_from * apartments.area') 
}