與Rails 3中的遺留數據庫的簡單關聯？

Question

我正在使用舊版數據庫，並且還通過Rails guides on associations進行了讀取。

我有兩種模式。 A diary模型和animal模型。

diary.rb

class Diary < ActiveRecord::Base 
    establish_connection :premvet 

    attr_accessible :DiaryNo ,:DiaryName, :DiaryDate, :SlotHour, :TotalSlots, :BlockSlots, :BlockBooked, :FreeSlot, :BookedSlot 

    self.table_name = 'diary' 
    self.primary_key = 'DiaryNo' 

    has_many :animals, :foreign_key => 'DiaryQueue' 
end 

animal.rb

class Animal < ActiveRecord::Base 
    establish_connection :premvet 

    self.table_name = 'animal' 
    self.primary_key = 'PVID' 

    attr_accessible :AddedBy, :Age, :AnimalBFAmount, :AnimalBalance, :AnimalName, :Archive, :BillType, :Breed, :ChronicStatus, :Class, :Classification, :ClientKey, :Colour, :Date1, :DateOfBirth, :DateofBirth, :Dead, :DiaryQueue, :DiscField, :DrugsAtCost, :DrugsNoVAT, :ESDAmount, :ESDType, :FNote, :FirstRegisteredDate, :Height, :IDNumber, :Insured, :InsuredWith, :IsClient, :IsClientDate, :IsMaster, :LastBilledAmount, :LastBilledDate, :LastConsDate, :LastContributionDate, :LastPaidDate, :LastWeightDate, :Locked, :LoyaltyMultiplier, :LoyaltyPoints, :MR_Flag_0, :MR_Flag_1, :MR_Flag_10, :MR_Flag_11, :MR_Flag_12, :MR_Flag_13, :MR_Flag_14, :MR_Flag_15, :MR_Flag_2, :MR_Flag_3, :MR_Flag_4, :MR_Flag_5, :MR_Flag_6, :MR_Flag_7, :MR_Flag_7, :MR_Flag_8, :MR_Flag_9, :Mileage, :Neutered, :NextApptDate, :ORT, :OldSex, :Opt_Flag_0, :Opt_Flag_1, :Opt_Flag_2, :Opt_Flag_3, :Opt_Flag_4, :Opt_Flag_5, :Opt_Flag_6, :Opt_Flag_7, :PVID, :PreferredContact, :PreferredUser, :Ref1, :RefPrac, :ReferredBy, :SSDType, :SeenInPeriod, :SendBill, :Sex, :SiteAnimal, :Species, :Status, :SurcAmount, :SurcType, :SurgeryNumber, :TBU, :TOSAmount, :TOSDrugs, :TOSFees, :TOSType, :Weight 

    belongs_to :client, :foreign_key => 'ClientKey' 
    belongs_to :diary, :foreign_key => 'DiaryNo' 
end 

動物索引視圖

<% @animals_todaysappointments.each do |animal| %> 
    <tr> 
    <td><%= animal.id %></td>  
    <td><%= animal.AnimalName %></td> 
    <td><%= link_to animal.client.Surname, animal.client %></td>  
    <td><%= animal.Species %></td> 
    <td><%= animal.Breed %></td> 
    <td><%= animal.NextApptDate.strftime("%d %b. %Y - %H:%M") %></td>   
    <td><%= animal.DiaryQueue %> 
    <td><%= animal.diary.DiaryName %></td>  
    <td><%= link_to 'Show', animal %></td> 
    </tr> 
<% end %> 

，你可以SE E - 這是使用顯示DiaryQueue從動物表：

<td><%= animal.DiaryQueue %> 

，我試圖從與日記表顯示DiaryName：

<td><%= animal.diary.DiaryName %></td>  

這失敗，異常錯誤：

undefined method `DiaryName' for nil:NilClass 

@animals_todaysappointments方法如下所示：

def appointments 
    @animals_todaysappointments = Animal.where('DATE(NextApptDate) = ?', Date.today).page(params[:page]).per_page(15).order('NextApptDate ASC') 
    respond_to do |format| 
     format.html # index.html.erb 
    end 
    end 

如果我添加：

delegate :DiaryName, :to => :diary 

的動物模型，然後我得到以下錯誤：

Animal#DiaryName delegated to diary.DiaryName, but diary is nil: # 

每個動物記錄了0和10日記表之間的DiaryQueue值有許多行中，例行：

DiaryNo DiaryName DiaryDate SlotHour TotalSlots BlockBooked FreeSlot BookedSlot 
-------------------------------------------------------------------------------------- 
1  Morning 2012-07-16 9   18   0   0   18 

有與同DiaryNo行，但他們也有同樣的DiaryName。它只是在這些行中改變的DiaryDate，SlotHour，TotalSlots，BlockBooked，FreeSlot和BookedSlot。

要儘量防止我加了錯誤以下的觀點：

<% unless animal.DiaryName.nil? %> 
<td><%= animal.DiaryName %></td> 
<% else %> 
<td><%= animal.DiaryQueue %> 
<% end %> 

，但我得到一個異常：

Animal#DiaryName delegated to diary.DiaryName, but diary is nil: # 

我在做什麼錯？

Answer 1

鑑於以上您的回答，您可能需要在動物改變belongs_to的方法如下：

belongs_to :diary, :foreign_key => "DiaryQueue", :primary_key => "DiaryNo" 

在你目前的實現你的模型去嘗試匹配Animal#DiaryNo對Diary#DiaryNo，當你」 ve說你想要的是匹配Animal#DiaryQueue對Diary#DiaryNo。