我司做健康类网站，需求如下：有 Movement 与 Disease 两个 model，逻辑上它们是 has_and_belongs_to_many 关系，但此外有多一层需求，需要在对应关系上加一个 status，如：有些 Movement 对 Disease 有好的影响，也可能有不好的影响，这个时候 has_and_belongs_to_many 就不太适用了，我的做法如下： Movement model:

class Movement < ActiveRecord::Base

  has_many :disease_movment_restores, :class_name => "DiseaseMovement", :dependent => :destroy, :conditions => { :status => true }
  has_many :restores, :through => :disease_movment_restores, :source => "disease"

  has_many :disease_movment_taboos, :class_name => "DiseaseMovement", :dependent => :destroy, :conditions => { :status => false }
  has_many :taboos, :through => :disease_movment_taboos, :source => "disease"

end

Disease model:

class Disease < ActiveRecord::Base  
  acts_as_options  
end

为中间表创建模型 DiseaseMovement，它有自己的 id 字段

class DiseaseMovement < ActiveRecord::Base  
  set_table_name "diseases_movements"  
  belongs_to :disease  
  belongs_to :movement  
end

在 Movement edit 页面中：

<div class="box">
    <h3 class="hndle"><span>有助于恢复以下疾病</span></h3>
    <div class="inside">
        <%= f.select :restore_ids, Disease.find_as_options, {:include_blank => ""}, :class => "chzn-select-deselect", :multiple => "multiple", "data-placeholder" => "请选择疾病..." %>                
    </div>
</div> 

<div class="box">
    <h3 class="hndle"><span>疾病禁忌</span></h3>
    <div class="inside">
        <%= f.select :taboo_ids, Disease.find_as_options, {:include_blank => ""}, :class => "chzn-select-deselect", :multiple => "multiple", "data-placeholder" => "请选择疾病..." %>              
    </div>
</div> 

尤其要说明一下 edit 页面中我有使用 Chosen (https://github.com/harvesthq/chosenplugin，真心好用！) 这个

关于 Disease.find_as_options 这个东西，如果记录很多很多，可能就不太适合了！

效果见下图：

保存之后数据库中间表记录如下：

一直做前端，刚上手 ROR，希望大家多多指点！