数据库设计-Rails 3 has_many through有3个表

Question

我用这个来敲我的头，我问了一些类似的问题，但没有成功。所以我有三张表超级英雄、力量和团队。一个超级英雄可以拥有许多力量和团队，一种力量可以与许多超级英雄联系在一起，一个团队由许多超级英雄组成。我决定把这些保存到一个大的关系表（我称之为漫威）中

以下是我设置的：

class Superhero < ActiveRecord::Base
  attr_accessible :name, :power_ids, :team_ids, :attributes_marvels
  has_many :marvels, :dependent => :destroy
  has_many :powers, :through => :marvels
  has_many :teams, :through => :marvels
  accepts_nested_attributes_for :marvels
end
class Power < ActiveRecord::Base
  attr_accessible :name
  has_many :marvels, :dependent => :destroy
end
class Team < ActiveRecord::Base
  attr_accessible :name
  has_many :marvels, :dependent => :destroy
end
class Marvel < ActiveRecord::Base
  attr_accessible :power_id, :superhero_id, :team_id
  belongs_to :superhero
  belongs_to :power
  belongs_to :team
end

这是创造超级英雄的形式：

<%= form_for(@superhero) do |f| %>
 <div class="field">
  <%= f.label :name %><br />
  <%= f.text_field :name %>
 </div>
<div class="field">
 <p>Please select which team you work for:</p>
 <%= f.collection_select(:team_ids, Team.all(:order=>:name), :id, :name, {:prompt => true}) %>
 </div>
 <div class="field">
<p>Please check all powers that apply to you.</p>
<% Power.all.each do |power| %>
     <label class="checkbox">
     <%= check_box_tag "superhero[power_ids][]", power.id, @superhero.power_ids.include?(power.id) %>
     <%= power.name %>
    </label>
    <% end %>
 </div>
 <div class="actions">
  <%= f.submit %>
 </div>
<% end %>

超级英雄控制器

  def new
   @superhero = Superhero.new
  end
  def create
   @superhero = Superhero.new(params[:superhero])
  end

我之所以这样做，是因为我希望能够在表格中询问，（复选框）权力列表，（下拉列表）团队列表，现在向我显示基于这些标准的超级英雄列表。

我已经差不多可以工作了，但在保存时遇到了问题，我在记录器文件中注意到它给了我这个：

Parameters: {"utf8"=>"✓", "authenticity_token"=>"sgD0NIjDM8QhMdzSsb7M/+PFd+FxMtNeOGukrdw9qFA=", "superhero"=>{"name"=>"Storm", "team_ids"=>"3", "power_ids"=>["1"]}, "commit"=>"Create Superhero"}
INSERT INTO "superheros" ("created_at", "name", "updated_at") VALUES (?, ?, ?)  [["created_at", Thu, 07 Feb 2013 19:59:24 UTC +00:00], ["name", "Storm"], ["updated_at", Thu, 07 Feb 2013 19:59:24 UTC +00:00]]
INSERT INTO "marvels" ("created_at", "power_id", "superhero_id", "team_id", "updated_at") VALUES (?, ?, ?, ?, ?)[0m  [["created_at", Thu, 07 Feb 2013 19:59:24 UTC +00:00], ["power_id", nil], ["superhero_id", 8], ["team_id", 3], ["updated_at", Thu, 07 Feb 2013 19:59:24 UTC +00:00]]
INSERT INTO "marvels" ("created_at", "power_id", "superhero_id", "team_id", "updated_at") VALUES (?, ?, ?, ?, ?)  [["created_at", Thu, 07 Feb 2013 19:59:24 UTC +00:00], ["power_id", 1], ["superhero_id", 8], ["team_id", nil], ["updated_at", Thu, 07 Feb 2013 19:59:24 UTC +00:00]]

为什么它要插入两次，当你可以清楚地看到参数中的值时，为什么会有零值？

Answer 1

您需要在表的两侧创建依赖关系：

class Superhero < ActiveRecord::Base
  attr_accessible :name, :power_ids, :team_ids, :attributes_marvels
  has_many :marvels, :dependent => :destroy
  has_many :powers, :through => :marvels
  has_many :teams, :through => :marvels
  accepts_nested_attributes_for :marvels
end
class Power < ActiveRecord::Base
  attr_accessible :name
  `has_many :superheros, :through => :marvels`
  has_many :marvels, :dependent => :destroy
end
class Team < ActiveRecord::Base
  attr_accessible :name
  `has_many :superheros, :through => :marvels`
  has_many :marvels, :dependent => :destroy
end
class Marvel < ActiveRecord::Base
  attr_accessible :power_id, :superhero_id, :team_id
  belongs_to :superhero
  belongs_to :power
  belongs_to :team
end

通过这种方式，您可以在Marvels中为每个型号添加ID密钥，并且可以访问所有密钥，请在关联指南