Empty argument - form for - ruby-on-rails

Question

I want to implement a reset password functionality so I have followed this railscast, I receive the mail with the link to redirect to an edit password page but I get an error here.
View
<h1>Reset Password</h1>
<%= form_for #user, :url => password_reset_path(params[:id]) do |f| %>
<% if #user.errors.any? %>
<div class="error_messages">
<h2>Form is invalid</h2>
<ul>
<% for message in #user.errors.full_messages %>
<li><%= message %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="field">
<%= f.label :password %>
<%= f.password_field :password %>
</div>
<div class="field">
<%= f.label :password_confirmation %>
<%= f.password_field :password_confirmation %>
</div>
<div class="actions"><%= f.submit "Update Password" %></div>
<% end %>
The error is :First argument in form cannot contain nil or be empty
I'm assuming that #user is empty, I'm new on RoR and I don't know why I get this error
Password Controller
class PasswordResetsController < ApplicationController
def new
render :layout => false
end
def create
user = User.find_by_email(params[:email])
user.send_password_reset if user
redirect_to :connect, :notice => "An E-mail has been send"
end
def edit
render :layout => false
#user = User.find_by_password_reset_token!(params[:id])
end
def update
#user = User.find_by_password_reset_token!(params[:id])
if #user.password_reset_sent_at < 2.hours.ago
redirect_to new_password_reset_path, :alert => "Password ↵
reset has expired."
elsif #user.update_attributes(params[:user])
redirect_to root_url, :notice => "Password has been reset."
else
render :edit
end
end
end

Answer 1

Change your def edit to
def edit
#user = User.find_by_password_reset_token!(params[:id])
render :layout => false
end

Answer 2

you have to add
#user = User.new
to your new method.
you have also another error for your create method. there is no user creation.
class PasswordResetsController < ApplicationController
def new
#user = User.new
render :layout => false
end
def create
#user = User.new user_params
if #user.save
# your code to render success
else
# your code to render error
end
end
private
def user_params
params.require(:user).permit(:email) # add more
end
end

Answer 3

This is the answer to '#user.update_attributes(params[:user])' with forbidden attributes error.
Rails 4 has new feature known as strong parameters.
Change your password controller to:
class PasswordResetsController < ApplicationController
def new
render :layout => false
end
def create
user = User.find_by_email(params[:email])
user.send_password_reset if user
redirect_to :connect, :notice => "An E-mail has been send"
end
def edit
#user = User.find_by_password_reset_token!(params[:id])
render :layout => false
end
def update
#user = User.find_by_password_reset_token!(params[:id])
if #user.password_reset_sent_at < 2.hours.ago
redirect_to new_password_reset_path, :alert => "Password ↵
reset has expired."
elsif #user.update_attributes(user_params)
redirect_to root_url, :notice => "Password has been reset."
else
render :edit
end
end
private
def user_params
params.require(:user).permit(:name, :email_id, :password)
end
end