Question

My Rails app is generating this error whenever validation aren’t met:

undefined method `model_name' for NilClass:Class

post_controller.rb:

class PostsController < ApplicationController
  def index
    @posts = Post.all
  end

  def show
    @show_post = Post.find(params[:id])
  end

  def new
    @new_post = Post.new
  end



  def create
     @create_post = Post.new(params[:post])

     if @create_post.save
       redirect_to posts_path, :notice => "Your post was save"
       else
     render "new"
     end
  end




  def edit
    @edit_post = Post.find(params[:id])
  end


  def update
    @update_post = Post.find(params[:id])
    if @update_post.update_attributes(params[:post])
      redirect_to posts_path , :notice => "YOUR POST has been update"
    else
       render "edit"

    end

  end

  def destroy
    @destroy_post = Post.find(params[:id])
    @destroy_post.destroy
    redirect_to posts_path, :notice => "You succressfuly delete #{@destroy_post}"

  end
end

index.html.erb:

<h1>My blog</h1>

<% @posts.each do |post|%>
    <h2><%= link_to post.title, post%></h2>
    <p><%= post.content%></p>
    <p>
        <%= link_to "EDIT", edit_post_path(post)%>
        <%= link_to "Delete", post ,:confirm => "Are you sure?" , :method => :delete%>
    </p>
    <hr>
<% end%>

<p>
    <%= link_to "Add new post", new_post_path %>


</p>

post.rb:

class Post < ActiveRecord::Base
   attr_accessible :title, :content

   validates :title, :content, :presence => true
   validates :title, :length => { :minimum => 2}
   validates :title, :uniqueness =>true

end

The error is raised in the following context:

Extracted source (around line #2):

1: <h1>Add new post</h1>
2: <%= form_for @new_post do |form|%>
3:  <p>
4:      <%= form.label :title%><br />
5:      <%= form.text_field :title%>

I don’t think I have a problem with my code? Or the value is just nil and that’s why it comes with this error?

Answer 1

Stop doing this: @create_post, @new_post, @show_post, @edit_post etc, etc…

Start doing this: @post.

The problem is that your object is called @create_post in your create action. If the model is invalid, your create action is calling render "new". The “new” view expects @new_post to be set, which it isn’t. @new_post is nil, and form_for(nil) is raising an error. You should just be calling the variable @post in every method, there is no gain for naming them @create_post or @new_post. It adds meaningless clutter and, in this case, breaks things.