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Re^3: Predefining sub Parameters

by Tanktalus (Canon)
on Jun 22, 2005 at 23:30 UTC ( #469242=note: print w/replies, xml ) Need Help??


in reply to Re^2: Predefining sub Parameters
in thread Predefining sub Parameters

Actually, I find that validating my parms is actually less useful in perl than it was in other languages. That's largely because perl is soooo much better at DWIMmery than other languages.

For example, validating that the object you just got is a file handle is a complete waste of time. The object may be a glob reference, may be an IO::Handle (or derived) object, or may be something else tie'd to work like a file handle. Don't worry about it - just use it for reading or writing (as appropriate), and things work out great. If a wrong parm is passed in, you'll see that quickly enough ;-).

For another example, validating the the object you just got is a scalar is another waste of time. What if it's an object that has all the proper overloads so I can do some really funky stuff with it? You'll never believe what someone who is more skilled than you can get out of your module - don't stop them.

OTOH, validating user input from, say, the web, is of paramount importance. You're letting some arbitrary user who may be malicious use your computing resources, so you should be careful that they can't misuse them. Depends on what you're validating. In your case, it looks like the former, so you may be pleasantly surprised when suddenly the code you've been using for weeks or months in a certain way suddenly works wonderfully in another way.

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Re^4: Predefining sub Parameters
by willyyam (Priest) on Jun 23, 2005 at 13:22 UTC

    It's a good point. Damn Canadians and their logic ;-) I wasn't really trying to validate against type so much as by number, and having the first line of my sub definition be a hint as to its usage. I have the attention span of a hummingbird on crack, and I forget what my subs do and how to call them between uses in the same coding session. I also really like having sane variable names in my functions, and @_[1] is not, in my opinion, sane. Useful, but not sane.

      Validate by number? That's even easier. Seriously, go use Params::Validate when you want to do this sort of thing. Its simple enough for casual use and has enough bells and whistles to do heavy duty things too.

      use Params::Validate 'validate_pos'; sub foo { # Three args are required. my ( $foo, $bar, $baz ) = validate_pos( @_, 1, 1, 1 ); ... }

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