Question

我有以下设置

class Player < ActiveRecord::Base
  has_many :cards, :inverse_of => :player do
    def in_hand
      find_all_by_location('hand')
    end
  end
end

class Card < ActiveRecord::Base
  belongs_to :player, :inverse_of => :cards
end

这意味着以下工作：

p = Player.find(:first)
c = p.cards[0]
p.score # => 2
c.player.score # => 2
p.score += 1
c.player.score # => 3
c.player.score += 2
p.score # => 5

但以下行为方式不同：

p = Player.find(:first)
c = p.cards.in_hand[0]
p.score # => 2
c.player.score # => 2
p.score += 1
c.player.score # => 2
c.player.score += 2
p.score # => 3

d = p.cards.in_hand[1]
d.player.score # => 2

如何将:inverse_of关系扩展到扩展方法？（这只是一个错误吗？）

Answer 1

我找到了一个解决方法，如果（因为我）你愿意放弃Arel授予的SQL优化，只需在Ruby中完成。

class Player < ActiveRecord::Base
  has_many :cards, :inverse_of => :player do
    def in_hand
      select {|c| c.location == 'hand'}
    end
  end
end

class Card < ActiveRecord::Base
  belongs_to :player, :inverse_of => :cards
end

通过在Ruby中编写扩展名来过滤关联的完整结果，而不是缩小SQL查询，扩展返回的结果与:inverse_of的行为正确：

p = Player.find(:first)
c = p.cards[0]
p.score # => 2
c.player.score # => 2
p.score += 1
c.player.score # => 3
c.player.score += 2
p.score # => 5

d = p.cards.in_hand[0]
d.player.score # => 5
d.player.score += 3
c.player.score # => 8

Answer 2

它不起作用，因为＆＃34; in_hand＆＃34; method有一个返回数据库的查询。

由于inverse_of选项，工作代码知道如何使用已经在内存中的对象。

http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html

Rails :: inverse_of和Association扩展

2 个答案: