Rails 4 - Error Messages for Email Validation - ruby-on-rails

Question

I am saving an email to the database and then sending it. I am using the email model to validate the inputs, but I'm not sure how to display the error messages. I am getting an undefined method `errors' for nil:NilClass error for the fullmessage.errors.any? line in the index action(highlighted below)
View
<%= form_tag("/thank_you") do %>
<% if #fullmessage.errors.any? %> # <----- This line
<h3>Errors</h3>
<ul>
<% #fullmessage.errors.full_messages.each do |message| %> # Would also cause an error if exemption not already raised
<li><%= message %></li>
<% end %>
</ul>
<% end %>
<div class="row">
<div class="col-md-5">
<div class="form-group">
<%= text_field_tag :first_name, nil, class: 'form-control', placeholder: 'First Name' %>
</div>
</div>
<div class="col-md-7">
<div class="form-group">
<%= text_field_tag :last_name, nil, class: 'form-control', placeholder: 'Last Name' %>
</div>
</div>
</div>
<div class="row">
<div class="col-md-12">
<div class="form-group">
<%= text_field_tag :email, nil, class: 'form-control', placeholder: 'Email Address' %>
</div>
</div>
</div>
<div class="row">
<div class="col-md-12">
<div class="form-group text-area-wide">
<%= text_area_tag :message, nil, class: 'form-control text-area-wide', placeholder: 'When are you available?' %>
</div>
</div>
</div>
<%= submit_tag 'Get Started', class: 'btn btn-success' %>
<p>Skype required</p>
<% end %>
Controller
def thank_you
#first_name = params[:first_name]
#last_name = params[:last_name]
#email = params[:email]
#message = params[:message] || "Hello!"
#fullmessage = Email.create(first_name: #first_name, last_name: #last_name, email: #email, message: #message)
if #fullmessage.valid?
ActionMailer::Base.mail(
:from => #email,
:to => 'erikvdw#comcast.net',
:subject => "A new contact form message from #{#first_name} #{#last_name}",
:body => #message).deliver
else
redirect_to root_path
flash[:alert] = 'There was an issue with your submission'
end
end
Model
class Email < ActiveRecord::Base
validates_length_of :first_name, :maximum => 25, :minimum => 2
validates_length_of :first_name, :maximum => 30, :minimum => 2
validates_format_of :email, :with => /\A([^#\s]+)#((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i
validates_length_of :message, :maximum => 500, :minimum => 20
end

Answer 1

You have two options:
Use render instead of redirect to (this way you'll keep your #fullmessage object.
Save error into flash[:alert] and display it in the view
The 2nd option is more universal, you could add the relevant code to the layout and use it across the whole site. E.g.:
<% if !flash.empty? %>
<div id="flash">
<% flash.keys.each do |k| %>
<div class="alert alert-<%= k %>">
<%= flash[k] %>
</div>
<% end %>
</div>
<% end %>

Answer 2

Nil class means that the #fullmessage is nil and hasn't been set, and nil does not have the method errors, hence the error.
When you redirect, the #fullmessage value will have nothing because http is stateless. Absent caching and cookies, every variable is recreated with every request. think what you are trying to do is display the flash messages, if that is the case you can add the #fullmessage.errors to the flash and be able to display that on the redirect.