RubyonRails中使用多态性的替代方法

class CreateUserRequests < ActiveRecord::Migration
  def self.up
    create_table :user_requests do |t|
      t.string :string_data, :type
      t.integer :user_id, :integer_data
      t.timestamps
    end
  end
  def self.down
    drop_table :user_requests
  end
end


class UserRequest < ActiveRecord::Base
  belongs_to :user
end

class EmailAliasRequest < UserRequest
  validates_presence_of :string_data
  validates_format_of :string_data, :with => EMAIL_REGEX
end

class ProgramInstallRequest < UserRequest
  belongs_to :program, :class_name => "Program", :foreign_key => "integer_data"
  validates_presence_of :integer_data
end

class QuotaIncreaseRequest < UserRequest
  validates_presence_of :string_data
  validates_inclusion_of :string_data, :in => %w( 1GB 5GB 10GB 15GB )
end

string_data integer_data 到 email 或者其他什么让你的代码更有意义。让模型成为一个小黑匣子,把它全部隐藏起来。

我将使用多态关联,它允许一个模型属于使用单个关联的多个其他模型。大概是这样的:

class AdminRequest < ActiveRecord::Base
  belongs_to :user
  belongs_to :requestable, :polymorphic => true
end

class EmailAlias < ActiveRecord::Base
  has_many :admin_requests, :as => :requestable
end

class ProgramInstall < ActiveRecord::Base
  has_many :admin_requests, :as => :requestable
end

class QuotaIncrease < ActiveRecord::Base
  has_many :admin_requests, :as => :requestable
end

• Railscast 关于这个问题。