Ruby on Rails – 具有多个多对多关联的模型

Question

我目前正在 Ruby on Rails 3.2.1 中开发 Dungeons & Dragons 4th Edition Character Sheet 应用程序。我目前处于一个阶段，我意识到我需要将角色种族（矮人、精灵……）与能力奖励联系起来。 （例如：矮人作为种族特性在体质和智慧能力上获得 +2 加值。）

我目前有以下设置：

class Character < ActiveRecord::Base {
  has_many :attributions
  has_many :abilities, through: :attributions
}

class Attribution < ActiveRecord::Base {
  belongs_to :character
  belongs_to :ability

  # The "attributions" table also has the column "score,"
  # which is the character's ability score
}

class Ability < ActiveRecord::Base {
  has_many :attributions
  has_many :characters, through: :attributions
}

如您所见，每个角色都有自己的一套能力。我想我可以为角色竞赛做同样的事情，但我不确定这方面的任何最佳实践。我可能可以使用相同的连接模型，创建类似这样的东西（Character 将保持不变，除了覆盖 abilities 方法，也许）：

class CharacterRace < ActiveRecord::Base {
  # I am not sure if this will actually work, but I hope
  # you understand what I am trying to do with this
  has_many :racial_ability_traits, class_name: "Attribution"
  has_many :abilities, through: :racial_ability_traits
}

class Attribution < ActiveRecord::Base {
  # The following two are just like before
  belongs_to :character
  belongs_to :ability

  # This field would be new
  belongs_to :character_class
}

class Ability < ActiveRecord::Base {
  # These are the same as above
  has_many :attributions
  has_many :characters, through: :attributions

  # These would be new, and I am not sure if it will work, but
  # I hope you understand what I amm trying to do with this
  has_many :racial_traits, class_name: "Attribution"
  has_many :character_races, through: :racial_ability_traits
}

然而，即使 如果 这可行，我还是觉得为不同的连接使用相同的连接模型（即使目的几乎相同）是一种丑陋的方法。当然，我可以像这样创建不同类型的连接：

class CharacterRace < ActiveRecord::Base {
  has_many :abilities, through: :attributions

  # These are for the racial bonus
  has_many :racial_ability_bonuses
  has_many :abilities, through: :racial_ability_bonuses
}

class RacialAbilityBonus < ActiveRecord::Base {
  belongs_to :character_race
  belongs_to :ability
}

class Ability < ActiveRecord::Base {
  has_many :attributions
  has_many :abilities, through: :attributions

  # These are for the racial bonus
  has_many :racial_ability_bonuses
  has_many :character_races, through: :racial_ability_bonuses
}

这可能会起作用，但有一个问题。不仅种族可以具有这样的特征/奖励。一件魔法物品也可能提供能力加成。因此，Item 模型也应该被赋予has_many :abilities, through: :item_ability_bonus 关联。继续上面解释的道路，这将导致很多连接模型。

因此，我问你们是否知道处理这个问题的任何好方法。任何关于改进我现有代码的建议也是受欢迎的。

我非常感谢您认真的回答。 :-)

Answer 1

我想你只需要polymorphic associations。