ActiveRecord / Rails中的多列外键/关联

Question

我有徽章（类似于StackOverflow的徽章）。

其中一些可以附加到带有徽章的事物上（例如，帖子上附加了> X评论的徽章）。 几乎所有的标签都具有多个级别（例如，> 20，> 100，> 200），并且每个可标记x标记类型（= badgeset_id ）只能具有一个级别。

为了使执行每个徽章一个级别的约束更加容易，我希望徽章使用两列外键（ badgeset_id和level ）而不是主键（ badge_id ）来指定其徽章，尽管徽章确实具有标准主键也是。

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

我如何指定一个做到这一点的belongs_to关联（并且不尝试使用badge_id ），以便可以使用has_many :through ？

预计到达时间：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，条件用单引号引起来，而不是双引号，这使得它在运行时而不是加载时进行解释。

但是，当尝试将其与：through关联一起使用时，我得到undefined local variable or method 'level' for #<User:0x3ab35a8>的错误undefined local variable or method 'level' for #<User:0x3ab35a8> 。 似乎没有任何明显的效果（例如'badges.level = #{badgings.level}' ）...

ETA 2：提取EmFi的代码并对其进行一些清理。 它需要将badge_set_id添加到Badge，这是多余的，但是很好。

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

尽管这可行-并且可能是更好的解决方案-但我不认为这是对如何执行a）多键外键或b）与：through关联一起使用的动态条件关联问题的实际答案。 因此，如果有人对此有解决方案，请说出来。

Answer 1

如果将“徽章”分为两个模型，似乎最适合锻炼。 这是我将其分解以实现所需功能的方式。 我添加了一些命名作用域，以保持实际执行操作的代码的整洁。

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