undefined method `update' for nil:NilClass post scaffold - ruby-on-rails

Question

I am trying to update a post, and ever since I added the Redcarpet gem, I get an error when I try to update a post.
Here is the error: undefined method 'update' for nil:NilClass
Here is my posts controller:
class PostsController < ApplicationController
before_action :set_post, only: [:show, :edit, :update, :destroy]
# GET /posts
# GET /posts.json
def index
#posts = Post.all
end
# GET /posts/1
# GET /posts/1.json
def show
#post = Post.find_by_urlid(params[:urlid])
end
# GET /posts/new
def new
#post = Post.new
end
# GET /posts/1/edit
def edite
end
# POST /posts
# POST /posts.json
def create
#post = Post.new(post_params)
#post.urlid = SecureRandom.urlsafe_base64
respond_to do |format|
if #post.save
format.html { redirect_to #post, notice: 'Your Post was successfully created!' }
format.json { render :show, status: :created, location: #post }
else
format.html { render :new }
format.json { render json: #post.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /posts/1
# PATCH/PUT /posts/1.json
def update
respond_to do |format|
if #post.update(post_params)
format.html { redirect_to #post, notice: 'Your Post was successfully updated!' }
format.json { render :show, status: :ok, location: #post }
else
format.html { render :edit }
format.json { render json: #post.errors, status: :unprocessable_entity }
end
end
end
# DELETE /posts/1
# DELETE /posts/1.json
def destroy
#post.destroy
respond_to do |format|
format.html { redirect_to posts_url, notice: 'You have successfully deleted the Post!' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_post
#post = Post.find_by_urlid(params[:urlid])
end
# Never trust parameters from the scary internet, only allow the white list through.
def post_params
params.require(:post).permit(:urlid, :author, :title, :body, :likes, :dislikes, :tags)
end
end
I've look at other posts, and their answers don't work. Any ideas?
Edit:
Server Log:
Started PATCH "/posts/sfqm5y99cbomqh4nmuxq5w" for 127.0.0.1 at 2014-10-31 13:05:07 -0700
Processing by PostsController#update as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"FRRgB2pI6GAQa6YL8KLZrUShshjjGd7+IXrLv1hTi5E=", "post"=>{"author"=>"Un3qual", "title"=>"First post", "body"=>" on new *dev* system **:D**", "likes"=>"9999", "dislikes"=>"0", "tags"=>""}, "commit"=>"Update Post", "urlid"=>"sfqm5y99cbomqh4nmuxq5w"}
Post Load (0.1ms) SELECT "posts".* FROM "posts" WHERE "posts"."urlid" = 'sfqm5y99cbomqh4nmuxq5w' LIMIT 1
Completed 500 Internal Server Error in 1ms
NoMethodError (undefined method `update' for nil:NilClass):
app/controllers/posts_controller.rb:46:in `block in update'
app/controllers/posts_controller.rb:45:in `update'
Rendered /Library/Ruby/Gems/2.0.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/_source.erb (0.4ms)
Rendered /Library/Ruby/Gems/2.0.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (0.6ms)
Rendered /Library/Ruby/Gems/2.0.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (0.6ms)
Rendered /Library/Ruby/Gems/2.0.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (8.9ms)
Started PATCH "/posts/sfqm5y99cbomqh4nmuxq5w" for 127.0.0.1 at 2014-10-31 15:42:18 -0700
Processing by PostsController#update as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"FRRgB2pI6GAQa6YL8KLZrUShshjjGd7+IXrLv1hTi5E=", "post"=>{"author"=>"Un3qual", "title"=>"First post", "body"=>" on new *dev* system **:D**", "likes"=>"9999", "dislikes"=>"0", "tags"=>""}, "commit"=>"Update Post", "urlid"=>"sfqm5y99cbomqh4nmuxq5w"}
Post Load (0.3ms) SELECT "posts".* FROM "posts" WHERE "posts"."urlid" = 'sfqm5y99cbomqh4nmuxq5w' LIMIT 1
Completed 500 Internal Server Error in 4ms
NoMethodError (undefined method `update' for nil:NilClass):
app/controllers/posts_controller.rb:46:in `block in update'
app/controllers/posts_controller.rb:45:in `update'
Rendered /Library/Ruby/Gems/2.0.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/_source.erb (0.4ms)
Rendered /Library/Ruby/Gems/2.0.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (0.6ms)
Rendered /Library/Ruby/Gems/2.0.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (0.6ms)
Rendered /Library/Ruby/Gems/2.0.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (10.2ms)

Answer 1

"Post.find_by_urlid(params[:urlid])" code has deprecated "find_by_" method. Rails 4 has deprecated "find_by_" methods. [Link]: http://edgeguides.rubyonrails.org/4_0_release_notes.html
Try Using: Post.find_by(urlid: params[:urlid]).
There is a typo error in "edite" method.

Answer 2

Based on the comments to your question, this is happening because there is no record with this urlid.
You should change your callback (before_action) filter like this.
def set_post
#post = Post.find_by(urlid: params[:urlid])
redirect_to posts_path, flash: {error: "The post does not exists"} if #post.nil?
end
This will redirect to the index of the posts, with an error message (you should have a div for errors flashing in your layout or your templates for it to appear).
If the #post exists, then it will relay to the action normally.

Answer 3

If you're not using any preloader which instantiate #post variable then it's the problem. For update action you should have:
def update
#post = Post.find params[:id]
respond_to do |format|
if #post.update(post_params)
format.html { redirect_to #post, notice: 'Your Post was successfully updated!' }
format.json { render :show, status: :ok, location: #post }
else
format.html { render :edit }
format.json { render json: #post.errors, status: :unprocessable_entity }
end
end
end