class MessagesChannel < ApplicationCable::Channel  
  def subscribed
    stream_from "messages"
  end
end

(function() {
  this.App || (this.App = {});

  App.cable = ActionCable.createConsumer('/cable');

}).call(this);

ActionCable.server.broadcast('messages', message.to_json)

App.messages = App.cable.subscriptions.create('MessagesChannel', {  
  received: function(data) {
    var jsonObj = JSON.parse(data);
....

class User < ApplicationRecord
  validates_with UserBirthZalupaValidator
end

class UserBirthZalupaValidator < ActiveModel::Validator
  def validate(record)
    begin
      birth = Date.parse(record.birth_date.to_s)
      record.errors.add(:base, "zlpa") unless birth.between?(start_date, end_date)
    rescue StandardError => e
      Rails.logger.error("Full zlpa: #{e.inspect}")
    end
  end

  def start_date
    Date.new(1900,1,1)
  end

  def end_date
    Time.zone.today
  end
end