Rails 3-验证2个模型和附加警告?

我假设您的注册模式定义了接受的学生和等待名单上的学生。我还假设讲座模型有两个属性 available_seats 和 available_wait_space ,等待名单是先到先填的,如果名单满了学生会被拒绝,但实际座位会被讲师手动确认或拒绝。

我当然会建议不要在管制员级别做任何事情。这只是模特们的工作。

class Enrollment < ActiveRecord::Base
  belongs_to :student
  belongs_to :lecture

  validates_presence_of  :student_id, :lecture_id, :status
  validates_inclusion_of :status, :in => %w[waiting confirmed rejected]
  validate :must_fit_in_wait_list, :on => :create
  validate :must_fit_in_class,     :on => :update

  scope :waiting,   where(:status => 'waiting')
  scope :confirmed, where(:status => 'confirmed')
  scope :rejected,  where(:status => 'rejected')

  def must_fit_in_wait_list
    unless waiting.count < lecture.available_wait_space
      errors.add(:base, "The waiting list is full")
    end
  end

  def must_fit_in_class
    unless confirmed.count < lecture.available_seats
      errors.add(:status, "The seats are full")
    end
  end
end

顺便说一下,别忘了设置默认值 status 在你的迁移中“等待”。

我认为这是最好的处理模式。在我之前提出的一个问题中,我也遇到过类似的问题。

Validating :inclusion in rails based on parent Model's attribute value

谢谢埃德格伦的回答!我找到了另一个简单的解决方案:

validate do |enrollment|
  if(enrollment.lecture.availableSeats <= 0)
    enrollment.errors.add_to_base("This lecture is booked out.") if enrollment.lecture.waitListAvailable <= 0
  end
end

等待列表的警告在控制器中处理:

if @enrollment.save
  if @enrollment.confirmed?
    format.html { redirect_to(@lecture, :notice => 'Enrollment successfull.') }
    format.xml  { render :xml => @lecture, :status => :created, :location => @lecture }
  else
    format.html { redirect_to(@lecture, :alert => 'You're on the waiting list!') }
    format.xml  { render :xml => @lecture, :status => :created, :location => @lecture }
  end