Rails：使用 find 方法访问多态关系的连接表

Question

好的，我有一个通用的 TimeSlot 模型，它处理时间跨度的 start_at 和 end_at。几个模型由此派生，但我指的是这个问题中的一个：AppointmentBlock，它是Appointments 的集合。我想验证一个AppointmentBlock，以便在同一时间范围内没有为特定Employee 安排其他AppointmentBlocks。由于AppointmentBlock 与TimeSlot 具有多态关联，因此您必须通过TimeSlot 访问AppointmentBlock 和end_at，如下所示：appt_block.time_slot.start_at 这意味着我需要某种加入我的:conditions 进行我的find() 方法调用。到目前为止，这是我的代码：

#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

由于AppointmentBlock 没有start_at 或end_at 我如何加入time_slots 表以使这些条件起作用？

Answer 1

你可以在 find 上使用 :joins 参数，类似这样：

 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')