[英]Rails Model has_many with multiple foreign_keys
相对较新的rails并尝试使用具有name,gender,father_id和mother_id(2个父项)的单个Person模型来建模一个非常简单的族“树”。 下面基本上是我想要做的,但显然我不能重复:has_many中的孩子(第一个被覆盖)。
class Person < ActiveRecord::Base
belongs_to :father, :class_name => 'Person'
belongs_to :mother, :class_name => 'Person'
has_many :children, :class_name => 'Person', :foreign_key => 'mother_id'
has_many :children, :class_name => 'Person', :foreign_key => 'father_id'
end
是否有一种简单的方法可以将has_many与2个外键一起使用,或者根据对象的性别更改外键? 或者还有其他/更好的方式吗?
谢谢!
在IRC上找到一个似乎有效的简单答案(感谢雷达):
class Person < ActiveRecord::Base
belongs_to :father, :class_name => 'Person'
belongs_to :mother, :class_name => 'Person'
has_many :children_of_father, :class_name => 'Person', :foreign_key => 'father_id'
has_many :children_of_mother, :class_name => 'Person', :foreign_key => 'mother_id'
def children
children_of_mother + children_of_father
end
end
在Person模型上使用named_scopes执行以下操作:
class Person < ActiveRecord::Base
def children
Person.with_parent(id)
end
named_scope :with_parent, lambda{ |pid|
{ :conditions=>["father_id = ? or mother_id=?", pid, pid]}
}
end
我相信你可以使用:has_one实现你想要的关系。
class Person < ActiveRecord::Base
has_one :father, :class_name => 'Person', :foreign_key => 'father_id'
has_one :mother, :class_name => 'Person', :foreign_key => 'mother_id'
has_many :children, :class_name => 'Person'
end
我会在下班后确认并编辑这个答案; )
我更喜欢使用范围来解决这个问题。 像这样:
class Person < ActiveRecord::Base
belongs_to :father, :class_name => 'Person'
belongs_to :mother, :class_name => 'Person'
has_many :children_of_father, :class_name => 'Person', :foreign_key => 'father_id'
has_many :children_of_mother, :class_name => 'Person', :foreign_key => 'mother_id'
scope :children_for, lambda {|father_id, mother_id| where('father_id = ? AND mother_id = ?', father_id, mother_id) }
end
这个技巧可以让没有使用实例的孩子轻松获得:
Person.children_for father_id, mother_id
不是所述一般问题的解决方案(“has_many with many foreign keys”),但是,如果一个人可以是母亲或父亲,但不是两者,我会添加一个gender
列并继续
has_many :children_of_father, :class_name => 'Person', :foreign_key => 'father_id'
has_many :children_of_mother, :class_name => 'Person', :foreign_key => 'mother_id'
def children
gender == "male" ? children_of_father : children_of_mother
end
我对rails(3.2)中关联和(多个)外键的回答:如何在模型中描述它们,并编写迁移只适合你!
至于你的代码,这是我的修改
class Person < ActiveRecord::Base
belongs_to :father, :class_name => 'Person'
belongs_to :mother, :class_name => 'Person'
has_many :children, ->(person) { unscope(where: :person_id).where("father_id = ? OR mother_id = ?", person.id, person.id) }, class_name: 'Person'
end
有问题吗?
我一直在寻找相同的功能,如果你不想返回一个数组而是一个ActiveRecord::AssociationRelation
,你可以使用<<
而不是+
。 ( 参见ActiveRecord文档 )
class Person < ActiveRecord::Base
belongs_to :father, :class_name => 'Person'
belongs_to :mother, :class_name => 'Person'
has_many :children_of_father, :class_name => 'Person', :foreign_key => 'father_id'
has_many :children_of_mother, :class_name => 'Person', :foreign_key => 'mother_id'
def children
children_of_mother << children_of_father
end
end
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