Rails：使用find方法訪問多態關係連接表

Question

好吧，我有一個通用的TimeSlot模型，它處理start_at和end_at時間跨度。幾個模型來自這個，但我指的是在這個問題中的一個：AppointmentBlock這是Appointments的集合。我想驗證AppointmentBlock，以便在同一時間範圍內沒有其他AppointmentBlocks已經安排用於特定的Employee。由於AppointmentBlock有TimeSlot多態關聯，你有AppointmentBlock的start_at和end_at通過訪問TimeSlot像這樣：appt_block.time_slot.start_at這意味着，我需要有某種在我:conditions加入我的find()方法調用。這是我到目前爲止的代碼：

#inside my time_slot.rb model 
belongs_to :time_slot_role, :polymorphic => true 

 

#inside my appointment_block.rb model 
has_one :time_slot, :as => :time_slot_role, :dependent => :destroy 
validate :employee_not_double_booked 

def employee_not_double_booked 
    unless self.employee_id 
    # this find's condition is incorrect because I need to join time_slots to get access 
    # to start_at and end_at. How can I do this? 
    blocks = AppointmentBlock.find(:first, 
     :conditions => ['employee_id = ? and (start_at between ? and ? or end_at between ? and ?)', 
     self.employee_id, self.time_slot.start_at, self.time_slot.end_at, 
     self.time_slot.start_at, self.time_slot.end_at]) 
    # pseudo code: 
    # collect a list of appointment blocks that end after this 
    # apointment block starts or start before this appointment 
    # block ends that are also associated with this appointment 
    # blocks assigned employee 
    # if the count is great then 0 the employee has been double 
    # booked. 

    # if a block was found that means this employee is getting 
    # double booked so raise an error 
    errors.add "AppointmentBlock", 
     "has already been scheduled during this time" if blocks 
    end 
end 

由於AppointmentBlock沒有一個start_at或end_at我怎麼能與time_slots表讓這些條件下工作，加入？

Answer 1

你可以用：加入參數上發現，與此類似：

blocks = AppointmentBlock.find(:first, 
      :conditions => ['employee_id = ? and (time_slots.start_at between ? and ? or time_slots.end_at between ? and ?)', 
      self.employee_id, self.time_slot.start_at, self.time_slot.end_at, 
      self.time_slot.start_at, self.time_slot.end_at], 
      :joins => 'join time_slots on time_slots.time_slot_role_id = appointment_blocks.id')