控制器上nil：NilClass的未定义方法“保存”

Question

I am begging to learn ruby on rails and doing the following I am receiving the following errors:

NoMethodError in ArticlesController#create

undefined method `save' for nil:NilClass

It has to do with the @article.save

articles_controllers.rb

class ArticlesController < ApplicationController
 def new
   @article = Article.new
 end
 def create
 #render plain: params[:article].inspect
   @article = Article.new(article_params)
   @article.save
   redirect_to articles_show(@article)
 end
 private
   def article_params
   params.require(:article).permit(:tittle, :description)  
   end
 end

routes.rb

Rails.application.routes.draw do

root 'pages#home'

get 'about', to: 'pages#about'

resources :articles

end

new.html.erb

Create an article

<%= form_for @article do |f| %>

<p>
    <%= f.label :tittle %><br>
    <%= f.text_field :tittle %>
</p>
<p>
    <%= f.label :description %> <br>
    <%= f.text_area :description %>
</p>
<p>
    <%= f.submit %> 
</p>

<% end %>

Answer 1

undefined method `save' for nil:NilClass

This error means you are calling the save method on a NilClass object ie nil .

When you do this: @article.save , for some reason, @article is nil here and hence you get that error. Make sure you populate the @article object and then call: @article.save .

Check your Rails log and put some debugging prints like: puts @article.inspect before you try to save it or so.

Answer 2

The error is here:

def create
   @article = Article.new article_params
   @article.save # <- Error
   redirect_to articles_show(@article)
end

The error is caused by @article not being present when you call .save on it.

---

Your code looks good.

The error must be caused by some other part of your app - I'm thinking your model.

I would ensure you have the following:

#app/models/article.rb
class Article < ActiveRecord::Base
   #-> also make sure you have the appropriate datatable
end

This should allow you to invoke the .new method on the class, which will then allow you to call .save as well.

The error you have is likely either because you don't have your model (which is unlikely because Rails would have failed with an "unrecognized constant" error), or your datatable doesn't exist.