Accessing rails flash[:notice] in a model

I am trying to assign a message to flash[:notice] in a model observer.

This question has already been asked: Ruby on Rails: Observers and flash[:notice] messages?

However, I get the following error message when I try to access it in my model:

undefined local variable or method `flash' for #<ModelObserver:0x2c1742c>

Here is my code:

class ModelObserver < ActiveRecord::Observer
  observe A, B, C

  def after_save(model)
    puts "Model saved"
    flash[:notice] = "Model saved"
  end
end

I know the method is being called because "Model saved" is printed to the terminal.

Is it possible to access the flash inside an observer, and if so, how?

I needed to set flash[:notice] in the model to override the generic "@model was successfully updated".

This what I did

1. Created a virtual attribute in the respective model called validation_message
2. Then I set the virtual attribute in the respective model when needed
3. Used an after_action when this virtual attribute was not blank to override the default flash

You can see my controller and model how I accomplished this below:

class Reservation < ActiveRecord::Base

  belongs_to :retailer
  belongs_to :sharedorder
  accepts_nested_attributes_for :sharedorder
  accepts_nested_attributes_for :retailer

  attr_accessor :validation_code, :validation_messages

  validate :first_reservation, :if => :new_record_and_unvalidated

  def new_record_and_unvalidated
    if !self.new_record? && !self.retailer.validated?
      true
    else
      false
    end
  end

  def first_reservation
    if self.validation_code != "test" || self.validation_code.blank?
      errors.add_to_base("Validation code was incorrect") 
    else
      self.retailer.update_attribute(:validated, true)
      self.validation_message = "Your validation is successful and you will not need to do that again"
    end
  end
end

class ReservationsController < ApplicationController

  before_filter :authenticate_retailer!
  after_filter :validation_messages, :except => :index

  def validation_messages
    return unless @reservation.validation_message.present?

    flash[:notice] = @reservation.validation_message
  end
end

One possible refactor would be to move the actual message in a proper file (e.g. a locale) and pass to validation_message only the proper key.

Should you need more than one notice it's easy enough to turn validation_message into an array or a hash and call it validation_messages instead.