Sinatra file for wedding form

Wedding sinatra.rb

require "sinatra"
require "dm-core"
require "dm-validations"
require "json"

class RSVP
  include DataMapper::Resource
  property :id, Serial
  property :first_name, String, :nullable => false, :message => "first_name"
  property :last_name, String, :nullable => false, :message => "last_name"
  property :email, String
  property :attending, Boolean
  property :created_at, DateTime
end

RSVP.auto_migrate! unless RSVP.storage_exists?

post '/rsvp' do
  form = params["data"]
  @res = []
  @values = {}
  form.each_pair do |i, person|
    rsvp = RSVP.new
    rsvp.attributes = {
      :first_name => person["first_name"],
      :last_name => person["last_name"],
      :email => person["email"],
      :attending => person["attending"],
      :created_at => Time.now
    }
    @values.merge!({i => rsvp})
  end
  invalid = @values.select {|k, rsvp| !rsvp.valid?}
  if invalid == []
    @values.each_pair do |i, rsvp|
      rsvp.save
      @res.push({:index => i, :response => "success"})
    end
  else
    @values.each_pair do |i, rsvp|
      if rsvp.valid? 
      else
        @res.push({
          :index => i,
          :fn => rsvp.errors[:first_name].to_s,
          :ln => rsvp.errors[:last_name].to_s,
          :email => rsvp.errors[:email].to_s
        })
      end
    end
  end
  content_type :json    
  @res.to_json
end