Rails3-验证一对唯一的索引

class Enrollment < ActiveRecord::Base    
  validates_uniqueness_of :student_id, :scope => :lecture_id
end

如果您想在提交新的注册之前确定该对是否存在,那么您可以使用Ajax请求(我更喜欢使用jQuery的RJS)并检查它:

class Enrollment < ActiveRecord::Base    
  def self.pair_exists?(student_id, lecture_id)
    Enrollment.find_all_by_student_id_and_lecture_id(student_id, lecture_id).any?
  end
end

很抱歉打开了一个旧线程,但由于是2011年,我仍然找不到合适的验证器,所以我自己创建了一个:

class UniqueSetValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    setup record
    record.errors[attribute] << "- collection of fields [" + @fields + "] is not unique" if record.class.count(:conditions => @conditions) > 0
  end

  def check_validity!
    raise ArgumentError, "Must contain an array of field names' symbols" unless options[:in] && options[:in].respond_to?(:each)
  end

  private

  def setup record
    conditions  = []
    fields      = []

    options[:in].each do |field|
      conditions  |= [ field.to_s + " = '" + record[field].to_s + "'" ]
      fields      |= [ field.to_s ]
    end

    @conditions = conditions.join(" AND ")
    @fields     = fields.join(", ")
  end
end

your_rails_app/lib/unique_set_validator.rb

并在以下位置启用它:

your_rails_app/config/application.rb

通过添加此行:

config.autoload_paths += %W( #{config.root}/lib  )

validates :field, :unique_set => [ :field, :field2 ]

它将验证对[:field,:field2]的唯一性,任何错误都将返回到:field。我还没试过,但它应该能在两个以上的领域发挥作用。

我希望我没有弄糟任何事情,这会帮助别人。:)

试试这个!

validates_uniqueness_of :enrollment_id, student_id, :scope => [:student_id, :lecture_id], :lecture_id], :message => "combination of enrollment, student and lecture should be unique."

更新:

validates_uniqueness_of :student_id, :scope => [:lecture_id], :message => "combination of student and lecture should be unique."

沃迪在回答中的定义是正确的。