def sudo
  saved_current_user = current_user
  current_user = admin_user
  yield
  current_user = saved_current_user
end

And in a method, invoke it with

sudo do
  puts "Something done as admin user"
end

However I know this doesn't work because at the time the block is
passed, the binding is fixed to the defining context.

So the question is: what is the right way to achieve the desired result.
Where the desired result is to pass a block to a method to be executed
in a different context, without the caller having to know any of the
implementation details.

Thanks for any help,

Context = Struct.new :user

def sudo
   context = Context.new
   context.user = "admin_user"
   yield context
end

outer_context = Context.new
outer_context.user = "normal_user"
puts "I am #{outer_context.user}"

sudo do |context|
   puts "I am #{context.user}"
end

--Kip