way to handle validation in controller

rescue_from_validation_error.rb

# implement alternative way to handle form validation error, via rescue_from ActiveRecord::RecordInvalid
# use Record.create! and @record.update_attributes!
module RescueFromValidationError

  # usage: rescue_from_validation_error('@user')
  def rescue_from_validation_error(instance_variable_name, options = {})
    rescue_from ActiveRecord::RecordInvalid, :with => :handle_validation_error

    define_method(:handle_validation_error) do |e|
      instance_variable_set(instance_variable_name, e.record)
      respond_to do |format|
        format.html { render :action => (e.record.new_record? ? options[:form] || 'new' : options[:form] || 'edit') }
      end
    end
  end

end

way to handle validation in controller

rescue_from ActiveRecord::RecordInvalid, :with =>  
handle_validation_error

def create
  article = current_user.articles.create!(params[:article])
  flash[:notice] = "..."
  respond_to do |format|
    format.html { redirect_to root_path }
  end
end

private

def handle_validation_error(e)
  @article = e.record
  respond_to do |format|
    format.html { render :action => (@article.new_record? ? 'new' :  
'edit') }
  end
end 

with RescueFromValidationError module

class MyController < ApplicationController

  extend RescueFromValidationError
  rescue_from_validation_error('@user')

  def create
    @user = User.create! params[:user]
    flash[:notice] = "User successfully created"
    redirect_to @user
  end

end