ActiveRecord/Rails 中的多列外键/关联

Question

我有徽章（有点像 StackOverflow）。

其中一些可以附加到可标记的东西上（例如，帖子上 >X cmets 的徽章附加到帖子上）。几乎所有都有多个级别（例如 >20、>100、>200），并且每个可徽章 x 徽章类型只能有一个级别 (= badgeset_id)。

为了更容易实施每徽章一级的约束，我希望徽章通过两列外键 - badgeset_id 和 level 指定其徽章 - 而不是通过主键 (@987654324 @)，虽然徽章也有一个标准的主键。

在代码中：

class Badge < ActiveRecord::Base
  has_many :badgings, :dependent => :destroy
  # integer: badgeset_id, level

  validates_uniqueness_of :badgeset_id, :scope => :level
end

class Badging < ActiveRecord::Base
  belongs_to :user
  # integer: badgset_id, level instead of badge_id
  #belongs_to :badge # <-- how to specify? 
  belongs_to :badgeable, :polymorphic => true

  validates_uniqueness_of :badgeset_id, :scope => [:user_id, :badgeable_id]
  validates_presence_of :badgeset_id, :level, :user_id  

  # instead of this:
  def badge
    Badge.first(:conditions => {:badgeset_id => self.badgeset_id, :level => self.level})
  end
end

class User < ActiveRecord::Base
  has_many :badgings, :dependent => :destroy do
    def grant badgeset, level, badgeable = nil
      b = Badging.first(:conditions => {:user_id => proxy_owner.id, :badgeset_id => badgeset,
        :badgeable_id => badgeable.try(:id), :badgeable_type => badgeable.try(:class)}) ||
        Badging.new(:user => proxy_owner, :badgeset_id => badgeset, :badgeable => badgeable)
      b.level = level
      b.save
    end
  end
  has_many :badges, :through => :badgings
  # ....
end

我如何指定一个belongs_to 关联来执行此操作（并且不尝试使用badge_id），以便我可以使用has_many :through？

ETA：这部分有效（即@badging.badge 有效），但感觉很脏：

belongs_to :badge, :foreign_key => :badgeset_id, :primary_key => :badgeset_id, :conditions => 'badges.level = #{level}'

请注意，条件是在单引号中，而不是双引号，这使得它在运行时而不是加载时被解释。

但是，当尝试将其与 :through 关联一起使用时，我收到错误 undefined local variable or method 'level' for #<User:0x3ab35a8>。而且没有什么明显的（例如'badges.level = #{badgings.level}'）似乎有效...

ETA 2：获取 EmFi 的代码并对其进行一些清理工作。它需要在徽章中添加badge_set_id，这是多余的，但是哦。

代码：

class Badge < ActiveRecord::Base
  has_many :badgings
  belongs_to :badge_set
  has_friendly_id :name

  validates_uniqueness_of :badge_set_id, :scope => :level

  default_scope :order => 'badge_set_id, level DESC'
  named_scope :with_level, lambda {|level| { :conditions => {:level => level}, :limit => 1 } }

  def self.by_ids badge_set_id, level
    first :conditions => {:badge_set_id => badge_set_id, :level => level} 
  end

  def next_level
    Badge.first :conditions => {:badge_set_id => badge_set_id, :level => level + 1}
  end
end

class Badging < ActiveRecord::Base
  belongs_to :user
  belongs_to :badge 
  belongs_to :badge_set
  belongs_to :badgeable, :polymorphic => true

  validates_uniqueness_of :badge_set_id, :scope => [:user_id, :badgeable_id]
  validates_presence_of :badge_set_id, :badge_id, :user_id  

  named_scope :with_badge_set, lambda {|badge_set|
    {:conditions => {:badge_set_id => badge_set} }
  }

  def level_up level = nil
    self.badge = level ? badge_set.badges.with_level(level).first : badge.next_level
  end

  def level_up! level = nil
    level_up level
    save
  end
end

class User < ActiveRecord::Base
  has_many :badgings, :dependent => :destroy do
    def grant! badgeset_id, level, badgeable = nil
      b = self.with_badge_set(badgeset_id).first || 
         Badging.new(
            :badge_set_id => badgeset_id,
            :badge => Badge.by_ids(badgeset_id, level), 
            :badgeable => badgeable,
            :user => proxy_owner
         )
      b.level_up(level) unless b.new_record?
      b.save
    end
    def ungrant! badgeset_id, badgeable = nil
      Badging.destroy_all({:user_id => proxy_owner.id, :badge_set_id => badgeset_id,
        :badgeable_id => badgeable.try(:id), :badgeable_type => badgeable.try(:class)})
    end
  end
  has_many :badges, :through => :badgings
end

虽然这可行 - 它可能是一个更好的解决方案 - 我不认为这是对如何执行 a) 多键外键或 b) 与 :through 一起使用的动态条件关联的问题的实际答案协会。因此，如果有人对此有解决方案，请说出来。

Answer 1

如果您将 Badge 分成两个模型，似乎锻炼效果最好。以下是我如何分解它以实现您想要的功能。我加入了一些命名范围来保持实际执行的代码干净。

class BadgeSet
  has_many :badges
end

class Badge
  belongs_to :badge_set
  validates_uniqueness_of :badge_set_id, :scope => :level

  named_scope :with_level, labmda {|level
    { :conditions => {:level => level} }
  }

  named_scope :next_levels, labmda {|level
    { :conditions => ["level > ?", level], :order => :level }
  }

  def next_level 
    Badge.next_levels(level).first
  end
end

class Badging < ActiveRecord::Base
  belongs_to :user
  belongs_to :badge 
  belongs_to :badge_set
  belongs_to :badgeable, :polymorphic => true

  validates_uniqueness_of :badge_set_id, :scope => [:user_id, :badgeable_id]
  validates_presence_of :badge_set_id, :badge_id, :user_id  

  named_scope :with_badge_set, lambda {|badge_set|
    {:conditions => {:badge_set_id => badge_set} }
  }

  def level_up(level = nil)
    self.badge = level ? badge_set.badges.with_level(level).first 
      : badge.next_level
    save
  end
end

class User < ActiveRecord::Base
  has_many :badgings, :dependent => :destroy do
    def grant badgeset, level, badgeable = nil
      b = badgings.with_badgeset(badgeset).first() || 
         badgings.build(
            :badge_set => :badgeset,
            :badge => badgeset.badges.level(level), 
            :badgeable => badgeable
         )

      b.level_up(level) unless b.new_record?

      b.save
    end
  end
  has_many :badges, :through => :badgings
  # ....
end