[英]In Rails, how do I create nested objects using accepts_nested_attributes_for?
In my Rails application, I am attempting to set up creation form for a TrainingClass
model. 在我的Rails应用程序中,我试图为
TrainingClass
模型设置创建表单。 I want this form to allow the user to create multiple ClassMeeting
models (which have a belongs_to relationship with the TrainingClass
model) within the same form, and I am using accepts_nested_attributes_for
to do this. 我希望此表单允许用户在同一表单内创建多个
ClassMeeting
模型(与TrainingClass
模型具有属植物关系),并且我正在使用accepts_nested_attributes_for
做到这一点。 Unfortunately, whenever I submit the form I get the error message: Meetings class can't be blank
. 不幸的是,每当我提交表单时,我都会收到错误消息:
Meetings class can't be blank
。
I realize that this is because ClassMeeting
has validates :class_id, presence: true
, and because TrainingClass
can't have an id until after it is saved, but I'm not sure of the right way to get around this. 我意识到这是因为
ClassMeeting
具有validates :class_id, presence: true
,并且因为TrainingClass
在保存之前无法拥有ID,但是我不确定解决此问题的正确方法。 (I can think of a few possible ways, but they aren't exactly elegant solutions.) Any ideas? (我可以想到几种可能的方法,但它们并不是精确的解决方案。)有什么想法吗? I'd appreciate any help you can give me.
谢谢您能给我的任何帮助。
Note: I realize quite a few questions similar to this have been asked in the past. 注意:我知道过去已经问过很多类似的问题。 However, most of those questions are old and have outdated answers, and none of them solved my problem.
但是,这些问题大多数都是过时的,并且答案已经过时,而且都没有解决我的问题。
Here is my code. 这是我的代码。 Keep in mind that although I have simplified some aspects of it for brevity, the relationship between the
ClassMeeting
and TrainingClass
models was left untouched: 请记住,尽管为简洁起见,我简化了某些方面,但
ClassMeeting
和TrainingClass
模型之间的关系保持不变:
ClassMeeting Model: ClassMeeting模型:
# == Schema Information
#
# Table name: class_meetings
#
# id :integer not null, primary key
# class_id :integer
# start :datetime
# end :datetime
# location :string(255)
# created_at :datetime not null
# updated_at :datetime not null
#
class ClassMeeting < ActiveRecord::Base
attr_accessible :start, :end, :location
validates :class_id, presence: true
validates :start, presence: true
validates :end, presence: true
validates :location, presence: true, length: {maximum: 255}
belongs_to :training_class, foreign_key: :class_id, inverse_of: :meetings
end
TrainingClass Model: TrainingClass模型:
# == Schema Information
#
# Table name: training_classes
#
# id :integer not null, primary key
# description :string(255)
# created_at :datetime not null
# updated_at :datetime not null
#
class TrainingClass < ActiveRecord::Base
attr_accessible :description, :meetings_attributes
validates :description, length: {maximum: 255}
has_many :meetings, class_name: :ClassMeeting, foreign_key: :class_id, inverse_of: :training_class
accepts_nested_attributes_for :meetings, allow_destroy: true
end
TrainingClasses Controller: TrainingClasses控制器:
class TrainingClassesController < ApplicationController
def new
@training_class = TrainingClass.new()
@training_class.meetings.build
end
def create
@training_class = TrainingClass.new()
if @training_class.update_attributes(params[:training_class])
redirect_to @training_class, notice: 'Class was successfully created.'
else
render "new"
end
end
end
TrainingClass Form (View): TrainingClass表格(查看):
<%= form_for @training_class do |f| %>
<%= render 'shared/error_messages', object: f.object %>
<%= f.text_area :description %>
<h2>Schedule</h2>
<%= f.fields_for :meetings do |meeting| %>
<%= meeting.label :start, "Start of Meeting:" %>
<%= meeting.text_field :start %>
<%= meeting.label :end, "End of Meeting:" %>
<%= meeting.text_field :end %>
<%= meeting.label :location, "Location:" %>
<%= meeting.text_field :location %>
<% end %>
<%= f.submit class:"btn btn-large btn-primary" %>
<% end %>
All right, I found the solution to my problem. 好的,我找到了解决问题的方法。 All I need to do is validate the presence of training_class instead of class_id in the
ClassMeeting
model. 我需要做的就是验证
ClassMeeting
模型中training_class的存在,而不是class_id的存在。 That way the existence of a training class is still validated, but the validator doesn't interfere with accepts_nested_attributes_for
's method of saving the model: 这样,仍然可以验证训练类的存在,但是验证器不会干扰
accepts_nested_attributes_for
的模型保存方法:
class ClassMeeting < ActiveRecord::Base
attr_accessible :start, :end, :location
validates :training_class, presence: true # :training_class instead of :class_id
validates :start, presence: true
validates :end, presence: true
validates :location, presence: true, length: {maximum: 255}
belongs_to :training_class, foreign_key: :class_id, inverse_of: :meetings
end
I pored over this example, trying out the differences with my code, but in the end my problem was fixed by using :inverse_of
. 我仔细研究了这个示例,尝试了与代码的差异,但最终,我的问题通过使用
:inverse_of
得以解决。
See accepts_nested_attributes_for child association validation failing 有关子关联验证失败的信息,请参见accepts_nested_attributes_
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