Caching Computations During Request Processing Even Better

In a recent post by Stefan Kaes from RailsExpress, Stefan mentions a method I have often used for speeding things up a bit.

module M
  def get_data_for(request)
    @cached_data_for_request ||=
      begin
        expensive computation depending on request returning data
      end
  end
end

However the problem with this method is that if get_data_for(request) returns nil, it will keep performing the request over and over again. Here is a slightly improved version if you don't always expect to get a return value.

module M
  def get_data_for(request)
    unless @cached_data_found
      @cached_data_found = true
      @cached_data_for_request =
        begin
          expensive computation depending on request returning data
        end
     end
     @cached_data_for_request
  end
end