4

我有两个模型通过连接表连接：

class Publication < ActiveRecord::Base
  attr_accessible :title, :author_attributes, :translator_attributes

  has_many :publication_contributors
  has_many :authors, :through => :publication_contributors, :source => :contributor,
    :conditions => {:publication_contributors => {:contributor_type => "Author"}}
  has_many :translators, :through => :publication_contributors, :source => :contributor,
    :conditions => {:publication_contributors => {:contributor_type => "Translator"}}

  accepts_nested_attributes_for :authors, :translators
end

class Contributor < ActiveRecord::Base
  attr_accessible :name

  has_many :publications, :through => :publication_contributors
  has_many :publication_contributors
end

class PublicationContributor < ActiveRecord::Base
  attr_accessible :contributor_type

  belongs_to :publication
  belongs_to :contributor
end

请注意，连接表有第三个属性（除了publication_id 和contributor_id），称为contributor_type。此属性可能包含诸如“作者”、“翻译者”、“编辑”或其他角色之类的角色。在我的发布模型中，我为两个更常见的贡献者类型“作者”和“翻译者”创建了一对关联。这些关联在检索相关数据方面表现良好，例如 with @publication.authors。但是，当通过嵌套形式创建这些关联时，它会出现问题。

我的表格看起来像这样：

<%= form_for @publication, :remote => true do |f| %>

  <%= f.label :title %>:
  <%= f.text_field :title %>

  <%= f.fields_for :authors do |builder| %>
    <%= builder.label :name, "Author" %>:
    <%= builder.text_field :name %>
  <% end %>

  <%= f.fields_for :translators do |builder| %>
    <%= builder.label :name, "Translator" %>:
    <%= builder.text_field :name %>
  <% end %>

  <%= f.submit %>
<% end %>

在我的控制器中：

def create
  publication = Publication.create(params[:publication])
end

表单按预期呈现，但在创建操作期间会出现问题。我曾希望 Rails 知道根据发布关联中的条件神奇地分配正确的contributor_type，例如：

has_many :authors, :through => :publication_contributors, :source => :contributor,
:conditions => {:publication_contributors => {:contributor_type => "Author"}}

不幸的是，事实并非如此。我在创建过程中收到此错误：

Mysql2::Error: Column 'contributor_type' cannot be null

这让我认为我唯一的办法是在before_create回调中手动分配contributor_type，但如果是这种情况，我如何确定要分配哪种类型？参数名称中有正确的类型，例如：

publication[authors_attributes][0][name]

有什么方法可以访问模型层中的信息吗？

更新：

我的new行动：

def new
  @publication = Publication.new
  publication_contributor = @publication.publication_contributors.build
  contributor = publication_contributor.contributor.build
end

它在最后一行（一个设置contributor）抛出此错误：

undefined method `build' for nil:NilClass
4

1 回答 1

6

你可以试试下面的吗？

class Publication < ActiveRecord::Base
  attr_accessible :title, :publication_contributors_attributes

  has_many :publication_contributors
  has_many :authors, through: :publication_contributors, source: :contributor, conditions: { publication_contributors: { contributor_type: 'Author' } }
  has_many :translators, through: :publication_contributors, source: :contributor, conditions: { publication_contributors: { contributor_type: 'Translator' } }

  accepts_nested_attributes_for :publication_contributors
end

class Contributor < ActiveRecord::Base
  attr_accessible :name

  has_many :publications, through: :publication_contributors
  has_many :publication_contributors
end

class PublicationContributor < ActiveRecord::Base
  attr_accessible :contributor_type

  belongs_to :publication
  belongs_to :contributor

  accepts_nested_attributes_for :contributor
end

<%= form_for @publication, :remote => true do |f| %>

  <%= f.label :title %>:
  <%= f.text_field :title %>

  <%= f.fields_for :publication_contributors do |pc_form| %>
    <%= pc_form.hidden_field :contributor_type %>
    <%= pc_form.fields_for :contributor do |c_form| %>
      <%= c_form.label :name, "Author" %>:
      <%= c_form.text_field :name %>
    <% end %>
  <% end %>

  <%= f.submit %>
<% end %>

更新：控制器代码

@publication.publication_contributors.build
@publication.publication_contributors.each do |pc|
  pc.build_contributor
end
于 2013-02-05T04:26:11.830 回答