Error: param is missing or the value is empty: thing - ruby-on-rails

Question

I'm using rails 4.0.8. I added a comment section to a model called 'Things', but I keep getting the same error "param is missing or the value is empty: thing" when I press the submit comment button. It says the error is in the Things#Controller. What am I doing wrong?
UPDATE: I removed the url path from the form, but a new error returns "Couldn't find Thing without an ID". The error is in Comments#Controller.
VIEW FOR THING/SHOW
<div id= "thing">
<h1>
<%= #thing.name %>
</h1>
<br>
<div id= "commentsection">
Comments
<div id= "comments">
<br>
<% #thing.comments.each do |c| %>
<%= c.username %>
<br>
<%= c.text %>
<% end %>
<%= form_for #comment, :url => thing_path do |f| %>
<%= f.label :username %>
<%= f.text_field :username %>
<%= f.label :comment %>
<%= f.text_field :text %>
<%= f.submit "Enter", class: "btn btn-small btn-primary" %>
<% end %>
</div>
</div>
</div>
THINGS CONTROLLER
class ThingsController < ApplicationController
def show
#thing = Thing.find(params[:id])
#thing.comments.build
#comment = Comment.new
end
def index
end
def new
#thing = Thing.new
#things = Thing.all
end
def create
#thing = Thing.new(thing_params)
if #thing.save
redirect_to #thing
else
render 'new'
end
end
private
def thing_params
params.require(:thing).permit(:name, :avatar)
end
end
COMMENTS CONTROLLER (I put asterisks around the line where the error is)
class CommentsController < ApplicationController
def show
#comment = Comment.find(params[:id])
end
def new
#comment = Comment.new
#comments = Comment.all
end
def create
****#thing = Thing.find(params[:thing_id])****
#comment = #thing.comments.create(comment_params)
redirect_to thing_path(#thing)
end
end
private
def comment_params
params.require(:comment).permit(:user, :text, :upvotes, :downvotes, :thing_id)
end
end
ROUTES
Website::Application.routes.draw do
get "comments/new"
get "comments/show"
get "things/new"
root 'home_page#home'
get "all/things/new" => 'things#new'
get "all/allthings"
resources :things
resources :good_comments
get "things/show"
get "things/results"
end

Answer 1

You are posting the #comment form to post '/things' path.
<%= form_for #comment, :url => thing_path do |f| %>
It should just be <%= form_for #comment do %> (Rails is smart enough to plug in the comments_path) or if you feel like being more explicit (even though it's not necessary)
<%= form_for #comment, url: :comments_path do %>
Another note though, if you want that Comment to be tied to that specific Thing then in your models it should be
Class Thing
has_many :comments
end
Class Comment
belongs_to :thing
end
Then make sure in your database comment has a thing_id foreign_key field and then your form for comment should actually look like
<%= form_for #thing, #comment do %>
<% end %>