Nested attributes not saving in database? Does not display values - Ruby on Rails

问题

I have a nested attribute and I can display values, but it is not saving into database why?

I have a model review and I want to nest attribute comments

review migration file

class CreateReviews < ActiveRecord::Migration
  def change
    create_table :reviews do |t|
      t.belongs_to :reviewable, polymorphic: true
      t.timestamps
    end
    add_index :reviews, [:reviewable_id, :reviewable_type]

  end
end

review model

class Review < ActiveRecord::Base
  attr_accessible :rating, :user_id, :comments_attributes, :service
  has_many :comments, as: :commentable
  belongs_to :user
  belongs_to :reviewable, polymorphic: true

  accepts_nested_attributes_for :comments

end

comments migration file

class CreateComments < ActiveRecord::Migration
  def change
    create_table :comments do |t|
      t.text :content
      t.belongs_to :commentable, polymorphic: true
      t.integer :user_id
      t.timestamps
    end
    add_index :comments, [:commentable_id, :commentable_type]
  end
end

comment model

class Comment < ActiveRecord::Base
  attr_accessible :content, :user_id
  belongs_to :commentable, polymorphic: true
  belongs_to :user
  belongs_to :review
end

This is the form

<%= form_for [@reviewable, @review], :html => {:multipart => true} do |f| %>

  <%= f.fields_for :comments, @review.comments.build do |field| %>
    <%= field.label "Comment" %></div>
    <%= field.text_field :content %>
  <% end %>

  <%= f.submit %>
<% end %>

It displays the fields, but how come when I save, it doesn't save?

I tried to display like this:

<%= @review.comments %>

Here's my review controller

  def new
    @review = @reviewable.reviews.new
    @review.comments.build
  end

Thanks for your help!

EDIT:

Review controller: create method

  def create
    @review = @reviewable.reviews.new(params[:review])
    @review.user = current_user
    if @review.save
      redirect_to @reviewable, notice: "review created."
    else
      render :new
    end
  end

回答1:

There seems to be some muddled logic in your controller and views

  def new
    @review = @reviewable.reviews.new
    @review.comments.build
  end

Here you are calling @reviewable.reviews.new, but @reviewable doesn't yet exist. A more usual way of calling this would be Review.new

Next in your view you do this

<%= form_for [@reviewable, @review], :html => {:multipart => true} do |f| %>

  <%= f.fields_for :comments, @review.comments.build do |field| %>

This is passing @reviewable and @review to the form_for. This seems odd. With nesting you would normally only need to pass the top level instance variable i.e. @review.

Next, when you get to fields_for you are passing :comments and @review.comments.build. Generally speaking this should only require :comment, because you've already built the comment in the controller.

I would recommend that you review these two screencasts

http://railscasts.com/episodes/196-nested-model-form-part-1 http://railscasts.com/episodes/197-nested-model-form-part-2

There are also a number of Gems that handle the whole process of making things commentable very eloquently, they can be found here

https://www.ruby-toolbox.com/categories/rails_comments

I think the commentable Gems path is better because they are being worked on by a larger community and I think end up being better than personal creations in the long term.

Hope this helps...

回答2:

you need to replace the following

<%= f.fields_for :comments, @review.comments.build do |field| %>

<%= f.fields_for :comments, @review.comments do |field| %>

to see created comments in form. As you have @review.comments.build in new action. Otherwise you cant see the associated comments on editing review

来源：https://stackoverflow.com/questions/17100462/nested-attributes-not-saving-in-database-does-not-display-values-ruby-on-rail

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