9

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

如何使:inverse_of关系扩展到扩展方法？（这只是一个错误吗？）

4

2 回答 2

7

如果（像我一样）您愿意放弃 Arel 授予的 SQL 优化并只在 Ruby 中完成所有操作，我已经找到了一种解决方法。

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

通过编写扩展以在 Ruby 中过滤关联的完整结果，而不是缩小 SQL 查询范围，扩展返回的结果在以下情况下表现正确:inverse_of：

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
于 2010-11-12T09:23:15.690 回答
4

它不起作用，因为“in_hand”方法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

于 2010-11-11T16:36:43.060 回答