Question

我遇到以下模型的一个小问题（在Rails 3.2rc1上）。所有权将项目和博客映射到用户（所有者），并且存在以不同方式处理所有权的不同类型的博客。

class User < ActiveRecord::Base
  has_many :ownerships, dependent: :destroy
  has_many :projects, through: :ownerships, source: :ownable, :source_type => 'Project'
  has_many :site_blogs, through: :ownerships, source: :ownable, :source_type => 'SiteBlog'
end

class Ownership < ActiveRecord::Base
  belongs_to :ownable, polymorphic: true
  belongs_to :owner, :class_name => 'User', foreign_key: 'user_id'
end

class Project < ActiveRecord::Base
  has_many :owners, through: :ownerships, as: :ownable
  has_many :ownerships, as: :ownable, dependent: :destroy
end

class Blog < ActiveRecord::Base
end  

class SiteBlog < Blog
  has_many :owners, through: :ownerships, as: :ownable
  has_many :ownerships, as: :ownable, dependent: :destroy
end

class ProjectBlog < Blog
  belongs_to :project
end

到目前为止一切正常，但SiteBlog#owners行为不端：

SiteBlog.first.owners
  SiteBlog Load (0.8ms)  SELECT "blogs".* FROM "blogs" WHERE "blogs"."type" IN ('SiteBlog') LIMIT 1
  User Load (1.4ms)  SELECT "users".* FROM "users" INNER JOIN "ownerships" ON "users"."id" = "ownerships"."user_id" WHERE "ownerships"."ownable_id" = 231145885 AND "ownerships"."ownable_type" = 'Blog'
=> []

问题是生成的SELECT的结尾："ownable_type" = 'Blog'。要使其工作，它应该是"ownable_type" = 'SiteBlog'，但是，我不知道如何教AREL这样做。

有什么想法吗？

Answer 1

我根据你的例子创建了一个小型rails应用程序。它工作正常。

User.create
SiteBlog.create
SiteBlog.first.owners << User.first

这会创建所有权记录

#<Ownership id: 5, ownable_id: 5, ownable_type: "Blog", user_id: 5, created_at: 2012-01-17 20:14:01", updated_at: "2012-01-17 20:14:01">

如您所见，ownable_type是“博客”，而不是“SiteBlog”。然后：

SiteBlog.first.owners
SiteBlog Load (0.3ms)  SELECT "blogs".* FROM "blogs" WHERE "blogs"."type" IN ('SiteBlog') LIMIT 1
User Load (0.3ms)  SELECT "users".* FROM "users" INNER JOIN "ownerships" ON "users"."id" = "ownerships"."user_id" WHERE "ownerships"."ownable_id" = 5 AND "ownerships"."ownable_type" = 'Blog'
=> [#<User id: 5, created_at: "2012-01-17 19:44:45", updated_at: "2012-01-17 19:44:45">]

所以 - 查询正在运行。

这是主要部分。查看activerecord / lib / activerecord / associations / association.rb：

def creation_attributes
  attributes = {}

  if reflection.macro.in?([:has_one, :has_many]) && !options[:through]
    attributes[reflection.foreign_key] = owner[reflection.active_record_primary_key]

    if reflection.options[:as]
      attributes[reflection.type] = owner.class.base_class.name
    end
  end

  attributes
end

具体来说，这一行告诉Rails应该写基类名称 - 即Blog，而不是SiteBlog：

attributes[reflection.type] = owner.class.base_class.name

所以 - 你的例子和Rails行为似乎都很好。

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1 个答案: