accepts_nested_attributes_for with hidden_field - ruby-on-rails

Question

Been searching stackoverflow for an answer to this one all day. I have a form to create a new topic. The first post should also be created with the topic. All is well except user_id is not being saved to the post.
Post Model
class Post < ActiveRecord::Base
belongs_to :topic
belongs_to :user
end
Topic Model
class Topic < ActiveRecord::Base
belongs_to :forum
belongs_to :user
has_many :posts
accepts_nested_attributes_for :posts
end
Post Controller
class PostsController < ApplicationController
def new
#post = Post.new
end
def create
#post = Post.new(post_params)
if #post.save
redirect_to topic_path(#post.topic_id)
else
render 'new'
end
end
private
def post_params
params.require(:post).permit(:content, :topic_id, :topic_name, :user_id)
end
end
Topic Controller
class TopicsController < ApplicationController
def new
#topic = Topic.new
#topic.posts.build
end
def create
#topic = Topic.new(topic_params)
if #topic.save
redirect_to #topic
else
render 'new'
end
end
private
def topic_params
params.require(:topic).permit(
:topic_name,
:forum_id,
:user_id,
posts_attributes: [:id, :content, :topic_id, :topic_name, :user_id ] )
end
end
new/topic View
<%= form_for(#topic) do |f| %>
<%= f.hidden_field :forum_id, :value => params[:forum_id] %>
<%= f.hidden_field :user_id, :value => current_user.id %>
<%= f.label :topic_name %>
<%= f.text_field :topic_name %>
<%= f.fields_for :posts do |p| %>
<%= p.label :content %>
<%= p.text_area :content %>
<% end %>
<%= f.submit "Post Topic", class: "btn btn-large btn-success" %>
<% end %>
I am not entirely sure why the user_id is not being passed to the post. Hopefully someone smarter than me can help me learn what to do :)
UPDATE
I changed the strong params in my topics controller to this.
def topic_params
params.require(:topic).permit(
:topic_name,
:forum_id,
posts_attributes: [:content, :topic_id, :id, '_destroy' ] ).merge(:user_id => current_user.id, posts_attributes: [:user_id => current_user.id])
end
Now the user_id is working but none of the posts_attributes like :content are being saved. I'm having a lot of fun with this one..

Answer 1

Notice the form attributes that being generated in the browser, all the nested attributes for post have a prefix like topic[post_attributes], try change the form to:
<%= form_for(#topic) do |f| %>
<%= f.hidden_field :forum_id, :value => params[:forum_id] %>
<%= f.label :topic_name %>
<%= f.text_field :topic_name %>
<%= f.fields_for :posts do |p| %>
<%= p.hidden_field :user_id, :value => current_user.id %>
<%= p.label :content %>
<%= p.text_area :content %>
<% end %>
<%= f.submit "Post Topic", class: "btn btn-large btn-success" %>
<% end %>

Answer 2

Short answer, user_id is not in the posts_attributes since the only attributes there is content, which means that allowing other attributes like topic_id and topic_name is useless.
Now that we cleared that, you SHOULD NOT use a form input for the value of the creator of any model, because it's easy for anyone to tamper with the form and set the value to anything else, like other user's id. Alternatively, you should set the user_id value in the controller, in your case, the TopicsController. Here is the code:
def create
_params = topic_params.deep_merge(user: current_user, posts_attributes: {user: current_user})
#topic = Topic.new(_params)
if #topic.save
redirect_to #topic
else
render 'new'
end
end
and remove the user_id hidden field from the form.
UPDATE: Your last code update contains an error; it should be .merge(:user_id => current_user.id, posts_attributes: {:user_id => current_user.id}). You used a square brackets around :user_id => current_user.id instead of curly ones.