This is the tenth part of the Twisted tutorial Twisted from Scratch, or The Evolution of Finger.
In this part, we separate the application code that launches a finger service from the library code which defines a finger service, placing the application in a Twisted Application Configuration (.tac) file. We also move configuration (such as HTML templates) into separate files.
Now this code, while quite modular and well-designed, isn't
properly organized. Everything above the application=
belongs in a
module, and the HTML templates all belong in separate files.
We can use the templateFile and templateDirectory attributes to indicate what HTML template file to use for each Page, and where to look for it.
organized-finger.tacNote that our program is now quite separated. We have:
We can also supply easy configuration for common cases with a makeService method that will also help build .tap files later:
finger_config.pyAnd we can write simpler files now:
simple-finger.tac% twisted -ny simple-finger.tac
Note: the finger user still has ultimate power: he can use makeService, or he can use the lower-level interface if he has specific needs (maybe an IRC server on some other port? maybe we want the non-SSL webserver to listen only locally? etc. etc.) This is an important design principle: never force a layer of abstraction: allow usage of layers of abstractions.
The pasta theory of design:
Ravioli, so one coarse-grain easily definable layer of abstraction on top of it all can be useful.