application.html.erb

<%= form_tag products_path, method: :get do %>
   <p>
      <%= text_field_tag :search, params[:search] %>
      <%= submit_tag "Search", title: nil %>
  </p>
<% end %>

product.rb

 def self.search(search)
    if search
      find(:all, :conditions => ['title LIKE ?', "%#{search}%"])
    else
      find(:all)
    end
  end

products_controller.rb

  def index
    @products = Product.search(params[:search])
    respond_to do |format|
      format.html
      format.json { render json: @products }
    end
  end


  def show
    @product = Product.find(params[:id])
    @cart = current_cart #Get current cart

    respond_to do |format|
      format.html
      format.json { render json: @product }
    end
  end