First argument in form cannot contain nil or be empty Hartl's Rails 4 Tutorial

Question

I'm working through Michael Hartl's Rails tutorial, and I'm running into an issue in section 7.3.3. I receive this error message:

ArgumentError in Users#new
Showing /Users/Anuraag/rails_projects/sample_app/app/views/users/new.html.erb where line #6 raised:
First argument in form cannot contain nil or be empty

when I run the following rspec:

bundle exec rspec spec/requests/user_pages_spec.rb -e "signup with invalid information"

at the following line:

<%= form_for(@user) do |f| %>

Here is my code. Please also let me know how I should improve this question if I'm not framing it well: I'm pretty new to StackOverflow as well

app/views/users/new.html.erb:

<% provide(:title, 'Sign up') %>
<h1>Sign up</h1>

<div class="row">
  <div class="span6 offset3">
    <%= form_for(@user) do |f| %>
      <%= render 'shared/error_messages' %>

      <%= f.label :name %>
      <%= f.text_field :name %>

      <%= f.label :email %>
      <%= f.text_field :email %>

      <%= f.label :password %>
      <%= f.password_field :password %>

      <%= f.label :password_confirmation, "Confirmation" %>
      <%= f.password_field :password_confirmation %>

      <%= f.submit "Create my account", class: "btn btn-large btn-primary" %>
    <% end %>
  </div>
</div>

app/assets/controllers/users_controller.rb:

class UsersController < ApplicationController
  def show
    @user = User.find(params[:id])
  end

  def create
    @user = User.new(user_params)
    if @user.save
      # Handle a successful save.
    else
      render 'new'
    end
  end

  private

    def user_params
      params.require(:user).permit(:name, :email, :password,
                                   :password_confirmation)
    end
end

spec/requests/user_pages_spec.rb

require 'spec_helper'

describe "User pages" do

  subject { page }

  describe "signup page" do
    before { visit signup_path }

    it { should have_content('Sign up') }
    it { should have_title(full_title('Sign up')) }
  end

  describe "profile page" do
    let(:user) { FactoryGirl.create(:user) }
    before { visit user_path(user) }

    it { should have_content(user.name) }
    it { should have_title(user.name) }
  end

  describe "signup" do

    before { visit signup_path }

    let(:submit) { "Create my account" }

    describe "with invalid information" do
      it "should not create a user" do
        expect { click_button submit }.not_to change(User, :count)
      end
    end

    describe "with valid information" do
      before do
        fill_in "Name",         with: "Example User"
        fill_in "Email",        with: "user@example.com"
        fill_in "Password",     with: "foobar"
        fill_in "Confirmation", with: "foobar"
      end

      it "should create a user" do
        expect { click_button submit }.to change(User, :count).by(1)
      end
    end
  end
end

Answer 1

The order of actions in controller file matters. I had the same error until I figure out the problem on order of action methods. Example. Controller file

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

def update

end

private
def post_params
    params.require(:post).permit(:title, :body)
end

I was working on edit action and was getting same error as you. The problem was I have written the edit action under private action. once I changed the order of this actions. It worked like a charm.

What I was trying to achieve ? I was trying to take the values of post instance variable and use it into html form.

Answer 2

In your new.html.erb you have specified form_for(@user) that means you need to have some value in instance variable @user before calling the new action.

You can do it in two ways :

one way is define an action new in your controller which would be called before rendering your new.html.erb layout. For eg:

def new
  @user = User.new
end

other way is that in your form itself you could specify something like

<%= form_for(User.new) do |f| %>

Defining it in your new action is more standard way of doing it.

Answer 3

I dont see a new action on you controller.

def new
  @user = User.new
end

I maybe made indirectly, but it couldn't hurt defining it yourself. From you title that may be why the @user variable is nil, it wasn't defined.