[jrockway]

Wait, I spend 99% of my time programming in dynamic languages, and I still use dependency injection. Why would I want to resort to hacks when I can just pass stuff in to my classes instead?

I will admit that I need the hacks from time to time, though. Recently, I wrote an overly large method that calls a callback when the command completes. For my test, I needed to run a bit of code right before the callback was called.

Runtime role application to the rescue! In my test, I wrote:

    my $done = AnyEvent->condvar;
    $done->begin;
    my $called_callback = 0;

    { pacakge FixupCallback;
      requires 'update_table';
      around 'update_table' => sub {
          my ($orig, $self, @args) = @_;
          my $cb = pop @args;

          # this is like "super"
          $self->$orig( @args, sub {
              $called_callback = 1;
              $cb->(@_);  # call the original callback
              $done->end; # then return control flow back to us
          });
      };
    }

Then, I just find the instance of the class that I need to tweak:

   my $view = $app->latency_publisher->view;
   FixupCallback->meta->apply($view);

And now I've fixed up the code enough to write a sane test. While cool, this doesn't negate the need for dependency injection. I want my app code to be 99% clean, and use the hacks for that 1% case where the hacks result in cleaner code than "the right way".

Also, I've never programmed Java or C#, so don't say that I have inherited bad habits from those languages :)