Where are instance variables in a Rails helper module stored?

Question

A tutorial I am following has in the subdirectory app/helpers the below SessionsHelper module which is used by many controllers and views. But where is the instance variable current_user stored when it is first created? What is the class of the object where it is stored?

When a controller first invokes the current_user method the current_user instance variable is created. When a view then invokes the current_user method how is it that a current_user instance variable is already present? Is self set to the controller object during the rendering of the view?

module SessionsHelper
  ...
  def current_user
    @current_user ||= User.find_by_remember_token(cookies[:remember_token])
  end
  ...
end

Answer 1

This answer tells in general about how instance variables are passed between controller and view: How are Rails instance variables passed to views?

So basically, if @current_user is set by a controller, that instance variable (along with all others) will be passed from your controller context on to the view context. If it has not been set by a controller, it will be set the first time a view uses it.

For more information, see the other answer. It is a good read.

Pasted from @mechanicalfish answer:

def view_assigns
  hash = {}
  variables  = instance_variables
  variables -= protected_instance_variables
  variables -= DEFAULT_PROTECTED_INSTANCE_VARIABLES
  variables.each { |name| hash[name[1..-1]] = instance_variable_get(name) }
  hash
end

Passing them to the view (github):

def view_context
  view_context_class.new(view_renderer, view_assigns, self)
end

Setting them in the view (github):

def assign(new_assigns) # :nodoc:
  @_assigns = new_assigns.each { |key, value| instance_variable_set("@#{key}", value) }
end