Polymorphic Commenting - ruby-on-rails

Question

I'm currently developing an app which allows users to post from their own account, but if they're an administrator of a group or venue, they can also post as that entity. I'm struggling converting the polymorphic association ideas from some of the other questions out there as generally they're all based around being able to comment on multiple things and not from multiple things.
I think my main issue is that I have my user's post form on the homepage, so it does not have an ID in the URL.
My post controller looks like this:
class PostsController < ApplicationController
before_action :authenticate_user!, only: [:create, :destroy]
before_filter :load_postable
def index
end
def new
#post = Postabe.posts.new(post_params)
end
def create
#post = #postable.posts.build(post_params)
if #post.save
flash[:success] = "Post created!"
redirect_to root_url
else
#feed_items = []
render 'static_pages/home'
end
end
def destroy
#post.destroy
redirect_to root_url
end
private
def post_params
params.require(:post).permit(:content)
end
def load_postable
resource, id = request.path.split('/')[1, 2]
resource_name = resource.singularize.classify
if resource_name == "User"
#postable = current_user
else
#postable = resource_name.constantize.find(id)
end
end
end
and my _post_form.html.erb partial:
<%= form_for ([#postable, #postable.post.new]), remote: true do |f| %>
<%= render 'shared/error_messages', object: f.object %>
<div class="field">
<%= f.text_area :content, placeholder: "Create a Post..." %>
</div>
<%= f.submit "Post", class: "btn btn-large btn-primary" %>
<% end %>
my related routes:
devise_for :users, :controllers => { :omniauth_callbacks => "omniauth_callbacks", :registrations => "registrations" }
resources :users, :only => [:index] do
member do
get :favourite_users, :favourited_users
end
resources :posts
end
resources :venues do
resources :posts
end
resources :groups do
resources :posts
end
Models as follows:
class Post < ActiveRecord::Base
belongs_to :postable, polymorphic: true
end
class User < ActiveRecord::Base
has_many :posts, as: :postable, dependent: :destroy
end
class Venue < ActiveRecord::Base
has_many :posts, as: :postable, dependent: :destroy
end
class Group < ActiveRecord::Base
has_many :posts, as: :postable, dependent: :destroy
end
It seems that I keep getting the error
Couldn't find Post without an ID
but I don't know why it's looking for a Post ID if it's not been created yet. Any help would be appreciated!

Answer 1

You have before_filter :load_postable in your controller. By default it will run for all the actions in your controller, even when the id is not specified. The error is thrown by #postable = resource_name.constantize.find(id), id is nil for index method.
Change this line to:
before_filter :load_postable, except: [:index]