Beefy Boxes and Bandwidth Generously Provided by pair Networks
Welcome to the Monastery
 
PerlMonks  

Re: Ingy's "Swiss Army Light Sabre" - or, "how do you design your APIs?"

by bart (Canon)
on Mar 24, 2004 at 23:25 UTC ( #339587=note: print w/ replies, xml ) Need Help??


in reply to Ingy's "Swiss Army Light Sabre" - or, "how do you design your APIs?"

My main objection to this module is that it's a catch-all for everything. If I do

my $foo = io('some/thing');
then, what is it? What do I expect it to be, a file, a directory? It can be either. It can even be something else entirely, I don't know.

Yet, later on, if it's a directory, I can do $foo->next, if it's a file, I can do $foo->slurp, but not vice versa.

This is the exact opposite of where strong typing wants to go: bugs aren't visible at compile time, it won't even complain at run time before you've already gone deep into the code: at the time of the next/slurp call.

I don't like this. If you want a dir, say so. If you want a file, idem ditto. The module shouldn't have to guess. Because the chances are, it guesses wrong.

No, I don't think one constructor io() for everything is a proper API.

Ideally, I'd like an io::dir() call to produce a directory thingy, and a io::file() call for a file. These look nice, but, as those a fully qualified names, thus you can't subclass them. io_dir() or io_file() don't look even half as nice.


Comment on Re: Ingy's "Swiss Army Light Sabre" - or, "how do you design your APIs?"
Select or Download Code
Re^2: Ingy's "Swiss Army Light Sabre" - or, "how do you design your APIs?"
by Aristotle (Chancellor) on Mar 25, 2004 at 03:41 UTC
    Exactly my thoughts. Thanks for putting into words and a simple example what I couldn't seem to, obvious as it may be in retrospect.

    Makeshifts last the longest.

Re: Re: Ingy's "Swiss Army Light Sabre" - or, "how do you design your APIs?"
by dragonchild (Archbishop) on Mar 25, 2004 at 04:03 UTC
    What about IO::All, instead of being a facade, instead is a factory?

    ------
    We are the carpenters and bricklayers of the Information Age.

    Then there are Damian modules.... *sigh* ... that's not about being less-lazy -- that's about being on some really good drugs -- you know, there is no spoon. - flyingmoose

Re: Re: Ingy's "Swiss Army Light Sabre" - or, "how do you design your APIs?"
by mvc (Scribe) on Mar 27, 2004 at 16:07 UTC

    My main objection:

    my $foo = io('some/thing');

    Yes it would be better to trap such a mistake ASAP. Would this be OK?

    my $foo = io(-filename => 'some/thing');

    You could even add some kind of policy enforcement aspect that will trap all dubious instantiations on runtime.

    I am not worried about a developer calling $foo->slurp when the intention was to use $foo as a directory, for the same reason that I am not worried about it being used as a Person object. It is just a coincidence that file and directory features are in the same physical package.

    BTW: The Java class java.io.File is also a file or a directory, and it implements some methods that are directory specific, like listFiles(). So it is a similar situation, despite the static typing. Of course that is a poor example, and anybody with a brain would use a util lib, e.g. the apache commons.

    It is leaky abstraction, but it looks like a pretty cool one to me! The freedom from having to check return values is a justification for this by itself.

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://339587]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others chilling in the Monastery: (17)
As of 2015-07-01 16:36 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









    Results (11 votes), past polls