Nested models and parent validation
I've got two models.
-Parent
has_many Children
;
- Parent
accepts_nested_attributes_for Children
;
class Parent < ActiveRecord::Base
has_many :children, :dependent => :destroy
accepts_nested_attributes_for :children, :allow_destroy => true
validates :children, :presence => true
end
class Child < ActiveRecord::Base
belongs_to :parent
end
I use validation to validate presence of children for every parent, so I can't save parent without children.
parent = Parent.new :name => "Jose"
parent.save
#=> false
parent.children_attributes = [{:name => "Pedro"}, {:name => "Emmy"}]
parent.save
#=> true
validation works. Then we will destroy children via _destroy
attribute:
parent.children_attributes = {"0" => {:id => 0, :_destroy => true}}
parent.save
#=> true !!!
parent.reload.children
#=> []
so I can destroy all children via nested forms and validation will pass.
Actually 开发者_C百科that happens because after I delete child from my parent via _delete
, children method still returns destroyed object before I reload it, so validation passed:
parent.children_attributes = {"0" => {:id => 0, :_destroy => true}}
parent.save
#=> true !!!
parent.children
#=> #<Child id:1 ...> # It's actually deleted
parent.reload.children
#=> []
Is it bug?
What is the question. The question is best solution to repair it. My approach is to add before_destroy filter to Child
to check if it is last one. But it makes system complicated.
This will probably work for you, but I have a feeling there's a much better answer out there. It sounds like a bug to me.
class Parent < ActiveRecord::Base
validate :must_have_children
def must_have_children
if children.empty? || children.all?(&:marked_for_destruction?)
errors.add(:base, 'Must have at least one child')
end
end
end
It's not a bug. Acording to the documentation
Validates that the specified attributes are not blank (as defined by Object#blank?)
and validates :children, :presence => true
is just the the same. The documentation doesn't say what happens if you try to use it on an association. You should use custom validation using validate
.
Using validates_presence_of
on has_many
association calls blank?
on association children
, which is an object of class Array. Since the blank?
is not defined for an Array
, it fires method_missing
which is caught inside Rails. Usually it do what you wants but I found it fails in Rails 3.1rc and Ruby 1.8.7 in a really awful way: it silently reverts the changes of associated records. It took me a couple of hours to find out what's happening.
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