嵌套集合可以有重复的子对象或多个parent_id/root/nodes吗？

发布于 2024-10-18 04:02:28 字数 139 浏览 3 评论 0原文

例如，我想创建一个可以管理零件和设备的应用程序。然而，特定设备也可以具有与其他设备相同的部件。

关于最好的方法有什么想法吗？

谢谢你！！！

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冷…雨湿花 2024-10-25 04:02:28

我认为您这里需要的是一个关联类来帮助建模多对多关系。在 Rails 中，这可能看起来像这样：

class Equipment < ActiveRecord::Base
  has_many :part_relationships
  has_many :parts, :through => :part_relationships
end

class Part < ActiveRecord::Base
  has_many :part_relationships
  has_many :equipment, :through => :part_relationships
end

class PartRelationship < ActiveRecord::Base
  belongs_to :equipment
  belongs_to :part
end

还有其他对此进行建模的方法（例如使用树类型结构），但如果“集合”是您想要的，那么这就是我要走的方式。

完成此操作后，您可以执行以下操作：

e = Equipment.find(:first)
e.parts # Returns all the parts on this equipment, including shared

p = Part.find(:first)
p.equipment # Returns all equipment this part features in.

# Create a new relationship between e and p
PartRelationship.create(:equipment => e, :part => p)

I think what you need here is an association class to help model the many-to-many relationship. In rails, this might look something like this:

class Equipment < ActiveRecord::Base
  has_many :part_relationships
  has_many :parts, :through => :part_relationships
end

class Part < ActiveRecord::Base
  has_many :part_relationships
  has_many :equipment, :through => :part_relationships
end

class PartRelationship < ActiveRecord::Base
  belongs_to :equipment
  belongs_to :part
end

There are other ways of modelling this (e.g. using a tree type structure), but if a 'set' is what you want, then this is the way I'd go.

Once this is done, you can do things like:

e = Equipment.find(:first)
e.parts # Returns all the parts on this equipment, including shared

p = Part.find(:first)
p.equipment # Returns all equipment this part features in.

# Create a new relationship between e and p
PartRelationship.create(:equipment => e, :part => p)

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