Ruby on rails 3 Rails：属于表上的列

我在看fb_graph api gem，它在迁移中有一些代码我想不出来，也就是说，对于列类型，它有

属于

，这不是典型的列类型

class CreateSubscriptions < ActiveRecord::Migration
  def self.up
    create_table :subscriptions do |t|
      t.belongs_to :facebook
      t.string :object, :fields, :verify_token
      t.text :history_json
      t.timestamps
    end
  end

  def self.down
    drop_table :subscriptions
  end
end

这里有一个指向Facebook.rb模型的链接

Facebook.rb

class Facebook < ActiveRecord::Base
  has_many :subscriptions

  def profile
    @profile ||= FbGraph::User.me(self.access_token).fetch
  end

  class << self
    extend ActiveSupport::Memoizable

    def config
      @config ||= if ENV['fb_client_id'] && ENV['fb_client_secret'] && ENV['fb_scope'] && ENV['fb_canvas_url']
        {
          :client_id     => ENV['fb_client_id'],
          :client_secret => ENV['fb_client_secret'],
          :scope         => ENV['fb_scope'],
          :canvas_url    => ENV['fb_canvas_url']
        }
      else
        YAML.load_file("#{Rails.root}/config/facebook.yml")[Rails.env].symbolize_keys
      end
    rescue Errno::ENOENT => e
      raise StandardError.new("config/facebook.yml could not be loaded.")
    end

    def app
      FbGraph::Application.new config[:client_id], :secret => config[:client_secret]
    end

    def auth(redirect_uri = nil)
      FbGraph::Auth.new config[:client_id], config[:client_secret], :redirect_uri => redirect_uri
    end

    def identify(fb_user)
      _fb_user_ = find_or_initialize_by_identifier(fb_user.identifier.try(:to_s))
      _fb_user_.access_token = fb_user.access_token.access_token
      _fb_user_.save!
      _fb_user_
    end
  end

end

class-FacebookENV['fb_client_secret']，
：scope=>ENV['fb_scope']，
：canvas\u url=>ENV['fb\u canvas\u url']
}
其他的
YAML.load_文件（“#{Rails.root}/config/facebook.yml”）[Rails.env]。符号化_键
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救援错误号：：enoint=>e
raise StandardError.new（“无法加载config/facebook.yml。”）
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def应用程序
FbGraph:：Application.new配置[：client\u id]，：secret=>config[：client\u secret]
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def auth（重定向_uri=nil）
FbGraph:：Auth.new config[：client\u id]，config[：client\u secret]，：redirect\u uri=>redirect\u uri
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def标识（fb_用户）
_fb_user_uu=通过_标识符（fb_user.identifier.try（：to_s））查找或初始化_
_fb\u用户\u.access\u令牌=fb\u用户.access\u令牌.access\u令牌
_fb\u用户\保存！
_fb_用户_
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你有很多问题一个问题，关于

的问题属于

，你可以在这里找到答案：

class Facebook < ActiveRecord::Base
  has_many :subscriptions

  def profile
    @profile ||= FbGraph::User.me(self.access_token).fetch
  end

  class << self
    extend ActiveSupport::Memoizable

    def config
      @config ||= if ENV['fb_client_id'] && ENV['fb_client_secret'] && ENV['fb_scope'] && ENV['fb_canvas_url']
        {
          :client_id     => ENV['fb_client_id'],
          :client_secret => ENV['fb_client_secret'],
          :scope         => ENV['fb_scope'],
          :canvas_url    => ENV['fb_canvas_url']
        }
      else
        YAML.load_file("#{Rails.root}/config/facebook.yml")[Rails.env].symbolize_keys
      end
    rescue Errno::ENOENT => e
      raise StandardError.new("config/facebook.yml could not be loaded.")
    end

    def app
      FbGraph::Application.new config[:client_id], :secret => config[:client_secret]
    end

    def auth(redirect_uri = nil)
      FbGraph::Auth.new config[:client_id], config[:client_secret], :redirect_uri => redirect_uri
    end

    def identify(fb_user)
      _fb_user_ = find_or_initialize_by_identifier(fb_user.identifier.try(:to_s))
      _fb_user_.access_token = fb_user.access_token.access_token
      _fb_user_.save!
      _fb_user_
    end
  end

end