Question

我正在尝试在Rails 4.0.1中的categories表和各种域模型（例如products和articles）之间建立多对多关联，使用:through => :categorizations模型捕获关系，基于this Railscast和the guides，但我在某处出错了。我收到的错误消息 - Unknown bind columns. We can account for this. - 对我来说似乎并不特别有用。我不知道下一步该往哪里去。

class Categorization < ActiveRecord::Base
  establish_connection "#{Rails.env}_sqlserver_api"

  self.primary_key = 'id'

  belongs_to :category
  belongs_to :product
  belongs_to :article
end

class Article < ActiveRecord::Base
  establish_connection "#{Rails.env}_sqlserver_api"

  self.primary_key = 'id'

  has_many :categorizations
  has_many :categories, :through => :categorizations
end

class Category < ActiveRecord::Base
  establish_connection "#{Rails.env}_sqlserver_api"

  self.primary_key = 'id'

  has_many :categorizations
  has_many :articles, :through => :categorizations
end

class ArticlesController < ApplicationController
  respond_to :json

  def index
    @articles = Article.limit(params[:limit]).offset(params[:offset])
    respond_with @articles, each_serializer: ArticleSerializer
  end

  def show
    @article = Article.find(params[:id])
    respond_with @article, serializer: ArticleSerializer
  end
end

categorizations表看起来像这样......

我还是Rails的新手，所以我觉得很有可能我错过了一些明显的东西，所以我想我会联系社区。

Answer 1

要使用categorized_type和categorized_id列设置多态关联，您必须执行以下操作：

class Categorization < ActiveRecord::Base
  establish_connection "#{Rails.env}_sqlserver_api"

  self.primary_key = 'id'

  belongs_to :category
  belongs_to :categorized, :polymorphic => true
end

class Article < ActiveRecord::Base
  establish_connection "#{Rails.env}_sqlserver_api"

  self.primary_key = 'id'

  has_many :categorizations, :as => :categorized
  has_many :categories, :through => :categorizations
end

class Category < ActiveRecord::Base
  establish_connection "#{Rails.env}_sqlserver_api"

  self.primary_key = 'id'

  has_many :categorizations
  has_many :articles, :through => :categorizations, :source => :categorized, :source_type => 'Article'
end

有关详细信息，请参阅http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html。

has_many：通过抛出“RuntimeError：未知的绑定列。我们可以解释这个。”

1 个答案: