NoMethodError when generating new view - ruby-on-rails

Question

I'm working on making a simple app that has users which can have many playlists. I'm trying to render the New view of a playlist but I'm getting this error:
NoMethodError in PlaylistsController#new
undefined method `playlist' for nil:NilClass
def new
#playlist = #user.playlist.new
end
Here's some context:
EDIT: I uploaded the relevant parts of my code to a gist.github:
https://gist.github.com/izikperz/164eab76e64d375d9075
Playlist_controller.rb
class PlaylistsController < ApplicationController
before_action :set_playlist, only: [:show, :edit, :update, :destroy]
:set_user
# GET /playlists
# GET /playlists.json
def index
#playlists = Playlist.all
end
# GET /playlists/1
# GET /playlists/1.json
def show
end
# GET /playlists/new
def new
#playlist = #user.playlist.new
end
# GET /playlists/1/edit
def edit
end
# POST /playlists
# POST /playlists.json
def create
#playlist = #user.playlists.new(playlist_params)
respond_to do |format|
if #playlist.save
format.html { redirect_to #user.playlist, notice: 'Playlist was successfully created.' }
format.json { render :show, status: :created, location: #playlist }
else
format.html { render :new }
#format.json { render json: #playlist.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /playlists/1
# PATCH/PUT /playlists/1.json
def update
respond_to do |format|
if #playlist.update(playlist_params)
format.html { redirect_to #playlist, notice: 'Playlist was successfully updated.' }
format.json { render :show, status: :ok, location: #playlist }
else
format.html { render :edit }
format.json { render json: #playlist.errors, status: :unprocessable_entity }
end
end
end
# DELETE /playlists/1
# DELETE /playlists/1.json
def destroy
#playlist.destroy
respond_to do |format|
format.html { redirect_to playlists_url, notice: 'Playlist was successfully destroyed.' }
format.json { head :no_content }
end
end
private
def set_user
#user = User.find_by(params[:user_id])
end
# Use callbacks to share common setup or constraints between actions.
def set_playlist
#playlist = Playlist.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def playlist_params
params.require(:playlist).permit(:user_id, :title, :img)
end
end
in my routes.rb I have:
resources :users do
resources :playlists
end
My user.rb model:
class User < ActiveRecord::Base
before_save { self.email = email.downcase }
has_secure_password
validates :password, length: { minimum: 6 }
has_many :playlists
end
Playlist.rb model:
class Playlist < ActiveRecord::Base
belongs_to :user, inverse_of: :playlist
validates :user_id, presence: true
end
My database schema:
ActiveRecord::Schema.define(version: 20141105043809) do
create_table "playlists", force: true do |t|
t.string "title"
t.string "img"
t.datetime "created_at"
t.datetime "updated_at"
t.integer "user_id"
end
create_table "users", primary_key: "user_id", force: true do |t|
t.string "name"
t.string "email"
t.datetime "created_at"
t.datetime "updated_at"
t.string "password_digest"
t.string "imgurl"
end
end
Anyone have any ideas?

Answer 1

The #user object in the new action is nil.
undefined method `playlist' for nil:NilClass
This is because params[:user_id] was not sent from your view.
Fix it by chaniging:
new_user_playlist_path(params[:user_id])
to:
new_user_playlist_path(user_id: params[:user_id])
After fixing that, another error will arise in the new action:
#playlist = #user.playlist.new
It should be pluralized as it is in your association:
#playlist = #user.playlists.new
#or
#playlist = #user.playlists.build
Or Simply ignore that:
#playlist = Playlist.new(user_id: #user.id)

Answer 2

Since the ActiveRecord Association between User and Playlist is :has_many and :belongs_to these are many to many associations. This implies that one user has more than one playlists. The association will provide you with a instance method #user.playlists not #user.playlist. Try to use the plural version. It should work.

Answer 3

Make sure that you are sending user_id along with form so that
#user = User.find_by(id: params[:user_id]) is not nil
and then change this
#playlist = #user.playlists.new