active record 如何实现上一个，下一个

Question

id不是挨个的，中间有不规则的空缺，如何找到上一个和下一个？

Answer 1

http://stackoverflow.com/questions/27...

class Page < ActiveRecord::Base
  def previous(offset = 0)    
    self.class.first(:conditions => ['id < ?', self.id], :limit => 1, :offset => offset, :order => "id DESC")
  end

  def next(offset = 0)
    self.class.first(:conditions => ['id > ?', self.id], :limit => 1, :offset => offset, :order => "id ASC")
  end
end