Rails 3.1 Scaffold undefined method `model_name' for nil:NilClass

Question

Help me StackOveflow, you're my only hope.

I'm getting the following error, and its driving me crazy.

NoMethodError in Players#new

Showing /home/paul/rails_projects/recruits/app/views/players/_form.html.haml where line #1 raised:

undefined method `model_name' for nil:NilClass

Extracted source (around line #1):

1: = form_for @player do |f|

2: -if @player.errors.any?

3: #error_explanation

4: %h2= "#{pluralize(@player.errors.count, "error")} prohibited this player from being saved:"

Trace of template inclusion: app/views/players/new.html.haml

Rails.root: /home/paul/rails_projects/recruits Application Trace | Framework Trace | Full Trace

app/views/players/_form.html.haml:1:in _app_views_players__form_html_haml___279577567_106102840' app/views/players/new.html.haml:3:in_app_views_players_new_html_haml__860668925_106567710' app/controllers/players_controller.rb:29:in `new'

I created this using the scaffold generator, which worked fine for me in another area, but not here apparently.

Here are the relevant files (the only change I've made to the files generated by the scaffold command was to add attr_accessable to the player model).

models/player.rb

class Player < ActiveRecord::Base 

  attr_accessible :first_name, :last_name, :scout_height, :scout_weight,
  :scout_profile_url, :scout_star_rating, :scout_overall_ranking,
  :scout_position_ranking, :scout_position, :espn_height, :espn_weight,
  :espn_profile_url, :espn_star_rating, :espn_overall_ranking,
  :espn_position_ranking, :espn_position, :rivals_height, :rivals_weight,
  :rivals_profile_url, :rivals_star_rating, :rivals_overall_ranking,
  :rivals_position_ranking, :rivals_position, :maxprep_height, :maxprep_weight,
  :maxprep_profile_url, :maxprep_star_rating, :maxprep_overall_ranking,
  :maxprep_position_ranking, :maxprep_position, :class, :school_commit, :loi_signed

end

controllers/players_controller.rb

class PlayersController < ApplicationController
  # GET /players
  # GET /players.json
  def index
    @players = Player.all

    respond_to do |format|
      format.html # index.html.erb
      format.json { render json: @players }
    end
  end

  # GET /players/1
  # GET /players/1.json
  def show
    @player = Player.find(params[:id])

    respond_to do |format|
      format.html # show.html.erb
      format.json { render json: @player }
    end
  end

  # GET /players/new
  # GET /players/new.json
  def new
    @player = Player.new

    respond_to do |format|
      format.html # new.html.erb
      format.json { render json: @player }
    end
  end

  # GET /players/1/edit
  def edit
    @player = Player.find(params[:id])
  end

  # POST /players
  # POST /players.json
  def create
    @player = Player.new(params[:player])

    respond_to do |format|
      if @player.save
        format.html { redirect_to @player, notice: 'Player was successfully created.' }
        format.json { render json: @player, status: :created, location: @player }
      else
        format.html { render action: "new" }
        format.json { render json: @player.errors, status: :unprocessable_entity }
      end
    end
  end

  # PUT /players/1
  # PUT /players/1.json
  def update
    @player = Player.find(params[:id])

    respond_to do |format|
      if @player.update_attributes(params[:player])
        format.html { redirect_to @player, notice: 'Player was successfully updated.' }
        format.json { head :ok }
      else
        format.html { render action: "edit" }
        format.json { render json: @player.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /players/1
  # DELETE /players/1.json
  def destroy
    @player = Player.find(params[:id])
    @player.destroy

    respond_to do |format|
      format.html { redirect_to players_url }
      format.json { head :ok }
    end
  end
end

views/players/new.html.haml

%h1 New player

= render 'form'

= link_to 'Back', players_path

views/players/_form.html.haml

= form_for @player do |f|
  -if @player.errors.any?
    #error_explanation
      %h2= "#{pluralize(@player.errors.count, "error")} prohibited this player from being saved:"
      %ul
        - @player.errors.full_messages.each do |msg|
          %li= msg

  .field
    = f.label :first_name
    = f.text_field :first_name
  .field
    = f.label :last_name
    = f.text_field :last_name
  .field
    = f.label :scout_height
    = f.number_field :scout_height
  .field
    = f.label :scout_weight
    = f.number_field :scout_weight
  .field
    = f.label :scout_profile_url
    = f.text_field :scout_profile_url
  .field
    = f.label :scout_star_rating
    = f.number_field :scout_star_rating
  .field
    = f.label :scout_overall_ranking
    = f.number_field :scout_overall_ranking
  .field
    = f.label :scout_position_ranking
    = f.number_field :scout_position_ranking
  .field
    = f.label :scout_position
    = f.text_field :scout_position
  .field
    = f.label :espn_height
    = f.number_field :espn_height
  .field
    = f.label :espn_weight
    = f.number_field :espn_weight
  .field
    = f.label :espn_profile_url
    = f.text_field :espn_profile_url
  .field
    = f.label :espn_star_rating
    = f.number_field :espn_star_rating
  .field
    = f.label :espn_overall_ranking
    = f.number_field :espn_overall_ranking
  .field
    = f.label :espn_position_ranking
    = f.number_field :espn_position_ranking
  .field
    = f.label :espn_position
    = f.text_field :espn_position
  .field
    = f.label :rivals_height
    = f.number_field :rivals_height
  .field
    = f.label :rivals_weight
    = f.number_field :rivals_weight
  .field
    = f.label :rivals_profile_url
    = f.text_field :rivals_profile_url
  .field
    = f.label :rivals_star_rating
    = f.number_field :rivals_star_rating
  .field
    = f.label :rivals_overall_ranking
    = f.number_field :rivals_overall_ranking
  .field
    = f.label :rivals_position_ranking
    = f.number_field :rivals_position_ranking
  .field
    = f.label :rivals_position
    = f.text_field :rivals_position
  .field
    = f.label :maxprep_height
    = f.number_field :maxprep_height
  .field
    = f.label :maxprep_weight
    = f.number_field :maxprep_weight
  .field
    = f.label :maxprep_profile_url
    = f.text_field :maxprep_profile_url
  .field
    = f.label :maxprep_star_rating
    = f.number_field :maxprep_star_rating
  .field
    = f.label :maxprep_overall_ranking
    = f.number_field :maxprep_overall_ranking
  .field
    = f.label :maxprep_position_ranking
    = f.number_field :maxprep_position_ranking
  .field
    = f.label :maxprep_position
    = f.text_field :maxprep_position
  .field
    = f.label :class
    = f.number_field :class
  .field
    = f.label :school_commit
    = f.text_field :school_commit
  .field
    = f.label :loi_signed
    = f.check_box :loi_signed
  .actions
    = f.submit 'Save'

routes.rb

Recruits::Application.routes.draw do

  resources :schools
  resources :players

  #get \"users\/show\"

  root :to => "home#index"

  devise_for :users
  resources :users, :only => :show
end

Answer 1

I'm guessing here but I believe it's because you gave your Player model an attribute called "class" you should change that to :player_class or something. class is a reserved word. You should also update your _form.html.erb and index.html.erb and show.html.erb files to use this new name.