複雜的ActiveRecord查詢

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我很難包裝我的頭如何構建此查詢。我不確定是否應該嘗試創建一堆範圍並嘗試鏈接它們。或者我把它放到類方法中？或者我會做兩個組合嗎？如果有人能給我一個簡短的例子，它會阻止我跳出窗口，我已經爲此工作了一個多星期了。複雜的ActiveRecord查詢

class CensusDetail < ActiveRecord::Base 
    belongs_to :apartment 
    belongs_to :resident 
end 

class Apartment < ActiveRecord::Base 
    belongs_to :apartment_type 
    has_many :census_details 
    has_many :residents, :through => :census_details 
end 

class ApartmentType < ActiveRecord::Base 
    has_many :apartments 
end 

class Resident < ActiveRecord::Base 
    has_many :census_details 
    has_many :apartments, :through => :census_details 
end 

apartment.rent_ready  = boolean value if apartment is ready 
apartment_type.occupany = the number of allowed occupants in an apartment 
census_detail.status  = either "past", "present", or "new" 
census_detail.moveout_date = date time resident is scheduled to move out

我需要建立一個查詢，執行以下操作：

- if the apartment is rent ready then do the following: 
- pull a list from census_details of all residents set as "current" for each apartment 
    -if the # of residents is less than the value of apartment_type.occupancy for this 
    apartment, then list it as available 
    -if the # of residents is = to the value of apartment_type.occupancy then 
    -does any resident have a scheduled move out date 
     -if not, do not list the apartment 
     -if yes, then list apartment

預先感謝任何幫助或建議。

來源

2013-04-12 Charlie May

我試過使用範圍和類方法。我明白如何創建兩者，但僅限於更簡單的查詢。在這裏，我首先獲取公寓清單，然後我需要逐個遍歷該清單，然後查詢census_details，將那裏找到的數字與apartment_type.occupancy中的值進行比較，從中做出更多決策。我不確定在使用示波器，方法或兩者的組合之間使用正確的軌道方式來構建軌道。我不希望任何人爲我寫代碼，更多的幫助如何解決這個問題。 –

讓我知道我是否在正確的軌道上，如果這是正確的方式，或者我弄得一團糟。這裏是我現在在做的： –

把範圍放在CensusDetail範圍內：resident_count， - >（id）{where（「status =？and apartment_id =？」，「current」，id）}'創建一個名爲可用的方法正在做上面列出的各種迭代，因爲我正在構建它，如果有必要，我正在創建範圍。我認爲這會起作用。如果是的話，我會發布代碼。如果我不在正確的軌道上，請告訴我。謝謝 –

我還沒有清理它，但這是爲我工作，所以我想分享。

apartment_type.rb

class ApartmentType < ActiveRecord::Base 
    has_many :apartments, :dependent => :nullify 
end

census_detail.rb

class CensusDetail < ActiveRecord::Base 
    belongs_to :resident_contacts 
    belongs_to :apartments 
    scope :get_current_residents, ->(id) { where("status = ? and apartment_id = ?", "current", id) } 
end

apartment.rb其中大部分工作正在發生

class Apartment < ActiveRecord::Base 
    belongs_to :apartment_type 
    has_many :census_details 
    has_many :residents, :through => :census_details 
    scope :rent_ready,  -> { where(:enabled => true) } 

    def self.available 
    available_apartments = [] 
    rent_ready_apartments = self.rent_ready.all 

    rent_ready_apartments.each do |apt| 
     tmp = ApartmentType.where('id = ?', apt.apartment_type_id).pluck(:occupancy) 
     occupancy = tmp[0] 
     current_residents = CensusDetail.get_current_residents(apt.id) 
     resident_count = current_residents.count 

     if resident_count < occupancy 
     available_apartments << apt 
     end 

     if resident_count = occupancy 
     scheduled = false 
     current_residents.each do |res| 
      if res.moveout_date 
      scheduled = true 
      end 
     end 
     if scheduled == true 
      available_apartments << apt 
     end 
     end 
    end 
    available_apartments 
    end 
end

的代碼是醜了一點，但其如此遠遠超過我的測試。我會編輯我原來的問題，而不是回答以防萬一有人有更好的方法來做這件事，但每次我做我的問題都會被拒絕。如果有人知道更好的方法，請讓我知道，因爲我在應用程序中有大約50個表的位置，現在它們都與複雜的查詢結合在一起。

來源

2013-04-13 17:28:23

複雜的ActiveRecord查詢

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