Proposed solution for controller / view communication.

controller.rb

class PapersController < ApplicationController

  def create
    @paper = Paper.new(params[:paper])

    if @paper.save
      redirect_to @paper, notice: :created
    else
      flash[:alert] = :invalid
      render action: :new
    end
  end

end

show.html.erb

<% if notice == :created %>
  <div class="alert-message block-message success fade in" data-alert="alert">
  <a class="close" href="#">×</a>
  <p>
    <strong>Well done!</strong> You successfully proposed a paper for wroc_love.rb conference.</p>
    <div>Please <strong>bookmark this page</strong> if you want to modify your proposal later</div>
    <div class="alert-actions">
      <%= link_to "Tweet about it!", "http://twitter.com/", :class => "btn small" %>
      <%= link_to "or not", request.path, :class => "btn small" %>
    </div>
  </div>
<% end %>

...