在 Rails 中，如何使用 accepts

本文介绍了在 Rails 中，如何使用 accepts_nested_attributes_for 创建嵌套对象?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

在我的 Rails 应用程序中，我试图为 TrainingClass 模型设置创建表单.我希望这个表单允许用户在同一个表单中创建多个 ClassMeeting 模型(它们与 TrainingClass 模型具有belongs_to 关系)，我正在使用 接受_nested_attributes_for 来做到这一点.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.

In my Rails application, I am attempting to set up creation form for a TrainingClass model. 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. Unfortunately, whenever I submit the form I get the error message: Meetings class can't be blank.

我意识到这是因为 ClassMeeting 有 validates :class_id,presence: true，并且因为 TrainingClass 直到保存后，但我不确定解决此问题的正确方法.(我可以想到几种可能的方法，但它们并不是完全优雅的解决方案.)有什么想法吗?如果您能给我任何帮助，我将不胜感激.

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. (I can think of a few possible ways, but they aren't exactly elegant solutions.) Any ideas? I'd appreciate any help you can give me.

注意:我意识到过去有人问过很多类似的问题.然而，这些问题中的大多数都是陈旧的，而且答案已经过时，而且没有一个能解决我的问题.

这是我的代码.请记住，虽然为了简洁起见我已经简化了它的某些方面，但是 ClassMeeting 和 TrainingClass 模型之间的关系没有受到影响:

Here is my code. 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:

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

培训班模型:

# == 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 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

培训班表格(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 %>

推荐答案

好的，我找到了问题的解决方案.我需要做的就是验证 ClassMeeting 模型中是否存在 training_class 而不是 class_id.这样，训练类的存在仍然被验证，但验证器不会干扰 accepts_nested_attributes_for 保存模型的方法:

All right, I found the solution to my problem. All I need to do is validate the presence of training_class instead of class_id in the ClassMeeting model. 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:

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