The idea here is to give you a simple method that can define your ivar for you, protecting against `nil` proactively, and record the location where the ivar was defined. Best part is, if someone looks for where `#expose` is defined, they'll be happy to find out it's not in a gem. Easy to modify/understand.

simple_exposing.rb

# Instead of ditching ivars, just make them easier to discover:

class ApplicationController < ActionController::Base
  
  private
  
  # Expose an object as an ivar to your views. Explodes if you try to assign nil.
  #
  # Use:
  #
  #   admin = Admin.find_by(email: "[email protected]")
  #
  #   expose(admin)                    # Defines @admin, because admin.class is Admin
  #   expose(admin, as: "@user")       # Overrides default ivar name
  #   expose(admin, permit_nil: true)  # Does *not* blow up if admin is nil
  #
  def expose(object, as: "@#{object.class.name.underscore}", permit_nil: false)
    if instance_variable_defined?(as)
      raise "Instance variable #{as} already defined!"
    end
    if object.nil? && permit_nil
      raise "Tried to expose #{as} as nil!"
    end
    unless Rails.env.production?
      exposed_variables[as] = OpenStruct.new(object: object, source: caller_locations[1])
    end
    instance_variable_set as, object
  end
  
  def exposed_variables
    # Add the underscores before and after to indicate that this variable is srs bsns.
    @__exposed_variables__ ||= {}
  end
  
  def source_for_ivar(ivar)
    exposed_variables.find { |k,v| v.object == ivar }.try(:source)
  end
end

# Usage

class OrdersController < ApplicationController
  def show
    order = Order.find(params[:id])
    expose order
  end
end

# When you want to override the name:

class OrdersController < ApplicationController
  def show
    order = PaypalOrder.find(params[:id])
    expose order, as: "@order"
  end
end

# Now, your view can go back to using ivars, knowing that @order will never be nil,
# and that if you ever need to know where it came from, you can find it.

# app/views/orders/show.html.erb
#
# <dl>
#   <dt>Order Number</dt>
#   <dt><%= @order.id %></dt>
# </dl>

Of course, this should really be a Concern

Also, nothing is stopping anyone on your project from not using #expose, but my aim was for the least invasive solution keeping to the "rails way."

expose(self) is probably a bad practice.