Undefined method m when using SimpleDelegator in Rails 4 - ruby-on-rails

Question

I was barking up the wrong tree with my original answer - I still have the problem but the plot thickens
I'm upgrading a Ruby 1.8.7/ Rails 3.0.20 project to Ruby 2.1.2 /Rails 4.1.8
In the code I have a class which delegates a number of instance methods.
class Account < ActiveRecord::Base
has_one :subscription
delegate :trial?, :payg? :to => :subscription
end
I have a decorator
class AccountOverview < SimpleDelegator
def self.for(account)
new(account)
end
def description
if payg?
'Pay As You Go'
elsif trial?
'Free Trial'
else
'Subscription'
end
end
end
Accessing the decorator from view gives the error message:
ActionView::Template::Error (undefined local variable or method `m' for ):
I hunted for an extraneous m, but can't find one.
I had thought that it was using the decorator ok for methods that didn't include delegated methods and that by defining the delegated functions within the class stopped the error:
def payg?
subscription.payg?
end
def trial?
subscription.trial?
end
However, it was not the case. What I was seeing was that a second attempt to render the view succeeds. But if I restart the server I get the error again.
I've tried the approach of instantiating SimpleDelegator as suggested, rather than deriving from it, and found that I could not access the methods in the original class.
Try this in the rails console:
class Test1
def testing
puts 'hi'
end
end
class Test2
def initialize(test)
SimpleDelegator.new(test)
end
def testing2
puts 'hello'
end
end
t = Test1.new
t.testing
hi
=> nil
h = SimpleDelegator.new(t)
h.testing
hi
=> nil
h = Test2.new(t)
h.testing
NoMethodError: undefined method `testing' for #<Test2:0x007fbea15d27a0>
But if instead I use
2.1.2 :008 > class Test2 < SimpleDelegator
2.1.2 :009?> def testing2
2.1.2 :010?> puts 'hello'
2.1.2 :011?> end
2.1.2 :012?> end
=> :testing2
2.1.2 :013 > h = Test2.new(t)
=> #<Test1:0x007fee090afc90>
2.1.2 :014 > h.testing
hi
=> nil
2.1.2 :015 > h.testing2
hello
=> nil
Also, I have found that the code that fails rendering in the view works in the console ( deriving from SimpleDelegator ):
a = Account.last
c = AccountOverview.new(a)
c.description
=> "Free Trial"
Reduced the classes to the very simplest
class AccountOverview < SimpleDelegator
def self.for(account)
new(account)
end
def description
'Pay As You Go'
end
class Account < ActiveRecord::Base
end
Still seeing the same error referring to missing method m
Created a brand new rails 4 project and added the same code and ran against the same db - this worked with no errors, so its something in my legacy setup.
Have given up and removed SimpleDelegator from the code and just used delegate to map the required functions to an instance variable for the base object and its now working. But not very satisfying.
class AccountOverview
delegate :payg?, :trial? :to => :#account
def initialize(account)
#account = account
end
def description
if payg?
'Pay As You Go'
elsif trial?
'Free Trial'
else
'Subscription'
end
end
end