[英]Ruby on Rails - nested attributes: How do I access the parent model from child model
I have a couple of models like so 我有几个这样的模特
class Bill < ActiveRecord::Base
has_many :bill_items
belongs_to :store
accepts_nested_attributes_for :bill_items
end
class BillItem <ActiveRecord::Base
belongs_to :product
belongs_to :bill
validate :has_enough_stock
def has_enough_stock
stock_available = Inventory.product_is(self.product).store_is(self.bill.store).one.quantity
errors.add(:quantity, "only #{stock_available} is available") if stock_available < self.quantity
end
end
The above validation so obviously doesn't work because when I'm reading the bill_items from nested attributes inside the bill form, the attributes bill_item.bill_id or bill_item.bill are not available before being saved. 上面的验证显然不起作用,因为当我从bill表单中的嵌套属性中读取bill_items时,属性bill_item.bill_id或bill_item.bill在保存之前不可用。
So how do I go about doing something like that? 那我该怎么做呢?
This is how I solved it eventually; 这就是我最终解决的问题; by setting parent on callback
通过在回调上设置父级
has_many :bill_items, :before_add => :set_nest
private
def set_nest(bill_item)
bill_item.bill ||= self
end
In Rails 4 (didn't test on earlier versions) you can access the parent model by setting the inverse_of
option on has_many
or has_one
: 在Rails 4中(未在早期版本上测试),您可以通过在
has_many
或has_one
上设置inverse_of
选项来访问父模型:
class Bill < ActiveRecord::Base
has_many :bill_items, inverse_of: :bill
belongs_to :store
accepts_nested_attributes_for :bill_items
end
Documentation: Bi-directional associations 文档: 双向关联
bill_item.bill应该可用,您可以尝试提升self.bill.inspect以查看它是否存在,但我认为问题出在其他地方。
I "fixed" it by setting parent in a callback: 我通过在回调中设置父“来修复”它:
class Bill < ActiveRecord::Base
has_many :bill_items, :dependent => :destroy, :before_add => :set_nest
belongs_to :store
accepts_nested_attributes_for :bill_items
def set_nest(item)
item.bill ||= self
end
end
class BillItem <ActiveRecord::Base
belongs_to :product
belongs_to :bill
validate :has_enough_stock
def has_enough_stock
stock_available = Inventory.product_is(self.product).store_is(self.bill.store).one.quantity
errors.add(:quantity, "only #{stock_available} is available") if stock_available < self.quantity
end
end
The set_nest method did the trick. set_nest方法完成了这个伎俩。 Wish it came standard with accepts_nested_attributes_for.
希望它与accepts_nested_attributes_for一起标准化。
Yeah, this kind of problem can be annoying. 是的,这种问题可能很烦人。 You could try adding a virtual attribute to your Bill Item model like this:
您可以尝试将虚拟属性添加到Bill Item模型,如下所示:
class BillItem <ActiveRecord::Base
belongs_to :product
belongs_to :bill
attr_accessible :store_id
validate :has_enough_stock
def has_enough_stock
stock_available = Inventory.product_is(self.product).store_is(load_bill_store).one.quantity
errors.add(:quantity, "only #{stock_available} is available") if stock_available < self.quantity
end
private
def load_bill_store
Store.find_by_id(self.store_id)
end
end
And then in your view you could add a hidden field like this: 然后在您的视图中,您可以添加如下隐藏字段:
<%= bill_item.hidden_field :store_id, :value => store_id %>
This hasn't been test but it might work. 这还没有测试,但它可能会起作用。 You might not find it desirable to have the store_id in the html but it may not be a concern.
你可能不会觉得在html中使用store_id是可取的,但它可能不是一个问题。 Let me know if this helps.
如果这有帮助,请告诉我。
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