Rails 4 controller actions for fields_for nested resources - ruby-on-rails

Question

I am trying to understand Rails' field_for, specifically what should go into the controller for nested resources. My issue is that when I create a comic with comic pages through the Comic form, the page's image are not saved.
I have Users, Comics, and ComicPages. Here are the models:
class User < ActiveRecord::Base
has_many :comics
has_many :comic_pages, through: :comics
end
class Comic < ActiveRecord::Base
belongs_to :user
has_many :comic_pages, :dependent => :destroy
accepts_nested_attributes_for :comic_pages
end
class ComicPage < ActiveRecord::Base
belongs_to :comic
end
Here is the form for Comic, where I also want to add comic_pages:
<%= form_for ([#user, #comic]) do |f| %>
<%= f.text_field :title %>
<%= f.fields_for :comic_pages do |comic_page| %>
<%= comic_page.file_field :comic_page_image %>
<% end %>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
I am confused about the comics_controller (new and create actions). How can I pass comic_page params to this controller???
def new
#user = current_user
#comic = #user.comics.new
#comic.comic_pages.build
end
def create
#user = current_user
#comic = #user.comics.new(comic_params)
#comic.comic_pages.build
respond_to do |format|
if #comic.save
format.html { redirect_to #user, notice: 'Comic was successfully created.' }
format.json { render action: 'show', status: :created, location: #user }
else
format.html { render action: 'new' }
format.json { render json: #comic.errors, status: :unprocessable_entity }
end
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_comic
#comic = Comic.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def comic_params
params.require(:comic).permit(:title, :synopsis)
end
def comic_page_params
params.require(:comic_page).permit(:comic_page_image, :comic_image_file_name)
end
Many thanks!
--- EDIT ---
After the answer for the params, I used it to create the following create action:
def create
#user = current_user
#comic = #user.comics.new(comic_params)
i = 0
until i = 1
#comic_page = #comic.comic_pages.new(comic_params[:comic_pages_attributes]["#{i}"])
#comic_page.save
i += 1
end
respond_to do |format|
if #comic.save
...
end
end
end

Answer 1

You need to permit those fields from comic_pages that you want to save through in the comic_params section of your controller
params.require(:comic).permit(:title, :synopsis, comic_pages_attributes: [:comic_page_image])