NoMethodError未定义的方法`'，用于nil：NilClass

Question

I'm novice with rails and starting with http://guides.rubyonrails.org/getting_started.html stucked in 5.7 Showing Articles with following error:

NoMethodError in Articles#show
Showing /home/jakub/workspace/blog/blog/app/views/articles/show.erb where line #3 raised:

undefined method `title' for nil:NilClass

Where the source is :

 <p>
    <strong>Title:</strong>
    <%= @article.title %>
  </p>

  <p>

and articles_controller.rb is:

class ArticlesController < ApplicationController

  def index
    @articles = Article.all
  end

  def create
    @article = Article.new(article_params)

    @article.save
    redirect_to @article
  end

  private
  def article_params
    params.require(:article).permit(:title, :text)
  end

  def show
    @article = Article.find(params[:id])
  end

end

and rake routes command brings:

        Prefix Verb   URI Pattern                  Controller#Action
welcome_contact GET    /welcome/contact(.:format)   welcome#contact
  welcome_index GET    /welcome/index(.:format)     welcome#index
       articles GET    /articles(.:format)          articles#index
                POST   /articles(.:format)          articles#create
    new_article GET    /articles/new(.:format)      articles#new
   edit_article GET    /articles/:id/edit(.:format) articles#edit
        article GET    /articles/:id(.:format)      articles#show
                PATCH  /articles/:id(.:format)      articles#update
                PUT    /articles/:id(.:format)      articles#update
                DELETE /articles/:id(.:format)      articles#destroy
           root GET    /                            welcome#index

Any idea what might cause this issue? Where should I look for ?

Answer 1

Your show action is private, therefore the instance variable @post cannot be used in the view. Move it to a public scope and the problem should be fixed.

Answer 2

1. Move your show action to public block.

2. undefined method `***' for nil:NilClass is actually shown when you are trying to access a object property which is actually not created yet.

3. Always check on view like this:

    @atrile.title if @article.title.present?