Example controller, view, schema and routes for including upvote/downvote functionality in Ruby on Rails.

controller.rb

def upvote
  @item = Item.find(params[:id])
  @item.upvotes += 1
  @item.save
  redirect_to items_path
end

routes.rb

Rails.application.routes.draw do
  resources :items do
    member do
      post :upvote
      post :downvote
    end
  end
    

schema.rb

create_table "items", force: :cascade do |t|
  t.string   "name"
  t.string   "author"
  t.integer  "upvotes",    default: 0
  t.integer  "downvotes",  default: 0
  t.datetime "created_at"
  t.datetime "updated_at"
end

view.erb

<%= link_to '▲', upvote_item_path(item), :data => {:method => "update"} %>