Rails 3.1 脚手架未定义方法“model_name”为 nil:NilClass

Posted 2023-02-23

【中文标题】Rails 3.1 脚手架未定义方法“model_name”为 nil:NilClass

【英文标题】：Rails 3.1 Scaffold undefined method `model_name' for nil:NilClass

【发布时间】：2011-11-16 15:36:04

【问题描述】：

帮助我 StackOveflow，你是我唯一的希望。

我收到以下错误，这让我发疯。

Players 中的 NoMethodError#new

显示 /home/paul/rails_projects/recruits/app/views/players/_form.html.haml 其中第 1 行提出：

nil:NilClass 的未定义方法 `model_name'

提取的源代码（第 1 行附近）：

1: = form_for @player do |f|

2: -if @player.errors.any?

3：#error_explanation

4: %h2= "#pluralize(@player.errors.count, "error") 禁止保存该玩家："

模板包含的痕迹：app/views/players/new.html.haml

Rails.root：/home/paul/rails_projects/recruits 应用程序跟踪 |框架跟踪 |全程跟踪

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'

我使用脚手架生成器创建了这个，它在另一个领域对我来说很好，但显然不是在这里。

这里是相关文件（我对脚手架命令生成的文件所做的唯一更改是将 attr_accessable 添加到播放器模型）。

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

控制器/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

【参考方案1】：

我在这里猜测，但我相信这是因为您为您的 Player 模型提供了一个名为“class”的属性，您应该将其更改为 :player_class 或其他内容。类是保留字。您还应该更新您的 _form.html.erb 和 index.html.erb 和 show.html.erb 文件以使用这个新名称。

【讨论】：

感谢 David，我已更改 Player 模型命名。我已经做了一些其他的事情来解决这个问题，但是回去这似乎可行，所以我很确定这是由于您的建议而不是我的其他解决方法。