validate.rb

class EventsController < ApplicationController
  def create
    @event = Event.new(event_params)
    
    if @event.valid_for_creation?
      @event.save
      redirect_to event_path
    else
      render :new
    end
  end
end

class Event < ActiveRecord::Base
  def valid_for_creation?
    add_errors(EventCreationValidatior.errors_for(self))
    errors.emtpy?
  end
end