link
有两个components
:componenta_id
和componentb_id
。为此,在Link
模型文件中我有:
belongs_to :componenta, class_name: "Component"
belongs_to :componentb, class_name: "Component"
validates :componenta_id, presence: true
validates :componentb_id, presence: true
validates :componenta_id, uniqueness: { scope: :componentb_id }
validates :componentb_id, uniqueness: { scope: :componenta_id }
在迁移文件中:
create_table :links do |t|
t.integer :componenta_id, null: false
t.integer :componentb_id, null: false
...
end
add_index :links, :componenta_id
add_index :links, :componentb_id
add_index :links, [:componenta_id, :componentb_id], unique: true
问题:这一切都有效。现在我希望componanta
和componentb
的组合是唯一的,无论它们的顺序如何。因此,不管哪个组件是componenta
哪个组件是componentb
(毕竟这是相同的链接;两个相同组件之间的链接)。因此,不应允许下面的两个记录,因为它们代表相同的链接,因此不是唯一的:
如何创建此唯一性验证?我有模型验证工作(见下文),但想知道是否以及如何在迁移/数据库级别添加验证...?
模型验证
我使用以下代码进行模型验证:
before_save :order_links
validates :componenta_id, uniqueness: { scope: :componentb_id }
private
def order_links
if componenta_id > componentb_id
compb = componentb_id
compa = componenta_id
self.componenta_id = compb
self.componentb_id = compa
end
end
以下测试证实了上述工作:
1. test "combination of two links should be unique" do
2. assert @link1.valid?
3. assert @link2.valid?
4. @link1.componenta_id = 3 #@link2 already has combination 3-4
5. @link1.componentb_id = 4
6. assert_not @link1.valid?
7. @link1.componenta_id = 4
8. @link1.componentb_id = 3
9. assert_raises ActiveRecord::RecordNotUnique do
10. @link1.save
11. end
12.end
迁移/数据库验证:
作为额外的安全级别,是否还有一种方法可以在db级别上对此进行验证?否则,仍然可以将以下两个记录写入数据库:componenta_id = 1 ; componentb_id = 2
以及componenta_id = 2 ; componentb_id = 1
。
答案 0 :(得分:4)
也许可以通过以下方式控制链接的创建:
def create_unique_link( comp_1, comp_2 )
if comp_1.id > comp_2.id
first_component = comp_1
second_component = comp_2
end
link = Link.find_or_create_by( componenta_id: first_comp.id, componentb_id: second_comp.id )
end
如果您需要验证,则可以自定义验证:
def ensure_uniqueness_of_link
if comp_1.id > comp_2.id
first_component = comp_1
second_component = comp_2
end
if Link.where( componenta_id: first_component.id, componentb_id: second_component ).first
errors.add( :link, 'Links should be unique' )
end
end
答案 1 :(得分:2)
validates :componenta_id, uniqueness: { scope: :componentb_id }
validates :componentb_id, uniqueness: { scope: :componenta_id }