PSGI and Object Oriented Programming

There is one thing that seems pretty simple - but it took me a bit of mulling over to fully understand

A PSGI application is a Perl code reference.

It is a reference to a sub that expects a hash ref representing the HTTP request passed to it as the one and only parameter and which returns an array ref representing a HTTP response. Hmm - yeah that's what web apps do - take the request and return the response.

But then you think - OK, but I like Object Oriented code and I want my application to be an object with attributes and stuff - so what can I do? Well - that is simple. Have your app as object as you like, and to the PSGI layer pass a closure referring to that object. For example if you application object normally handles the requests with a ->handle method then

	sub psgi_callback {
	my $self = shift;
	sub {
	my $req = Plack::Request->new( shift );
	$self->handle( $req );
	};
	}

view raw psgi_closure.pl hosted with ❤ by GitHub

would return a suitable callback. Which you can then use in your app.psgi file:

	use MyApp;
	my $app = MyApp->new();
	$app->psgi_callback;

view raw app.psgi.pl hosted with ❤ by GitHub

And this is exactly what I do in WebNano.