Re: Re^2: (nrd) Putting file contents into a scalar

For my own code, I even prefer to use IO::File because that gives me all that neat OO stuff on the file handle. And the additional benefit to be able to test for the type of a scalar which happens to be passed to me, by checking for ~~ref $fh eq 'IO::File'~~.

But that's much typing for oneliners...

Update: As merlyn correctly pointed out:

"Please don't do that. Your code is fragile. It will break when I pass an object that subclasses IO::File but acts in every way like an IO::File".

So I went through my latest and greatest module, which grossly offends against this statement, and quietly changed my test to read:

...
croak("Invalid type for 'outfile', missing method print()'")
  unless $outfile->can('print');
...
[download]

The immediate benefit is that I now can use IO::Scalar from my test script to get output in a variable instead of a file (or STDOUT). Cool!

--
Cheers, Joe

Comment on Re: Re^2: (nrd) Putting file contents into a scalar Select or Download Code

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Say no to ref $thing eq "Expected::Type" by merlyn (Sage) on Oct 29, 2002 at 14:35 UTC
And the additional benefit to be able to test for the type of a scalar which happens to be passed to me, by checking for `ref $fh eq 'IO::File'`. Please don't do that. Your code is fragile. It will break when I pass an object that subclasses `IO::File` but acts in every way like an `IO::File`. Instead, write your code so that the class doesn't matter. Use the polymorphism as it was intended. If you are unsure if `$object_x` can handle a particular method call, then use `UNIVERSAL::can` against it, or put it in an eval block to trap the potential error. The use of `ref` in ordinary code should be limited to determining whether something is a reference or not (such as whether the first parameter for a method call is a class or instance). Any explicit comparison will break subclassing. Too much "navel contemplation" is a bad thing in robust code. -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply]
Re: Say no to ref $thing eq "Expected::Type" by Felonious (Chaplain) on Oct 29, 2002 at 14:44 UTC
or use UNIVERSAL::isa() which will most easily accomplish what merlyn is talking about. [TINPC@perlcabal.com shh]$ su real	[reply]
•Re: Re: Say no to ref $thing eq "Expected::Type" by merlyn (Sage) on Oct 29, 2002 at 14:47 UTC
No, I meant "can" specifically. Suppose I come up with a type that doesn't inherit from `IO::File`, but has all the proper behaviors of `IO::File`. Why should you reject it? All you should care is that when you send `close` to it, it closes. Hence, `can` is more appropriate than `isa`, almost every time. Or, to avoid the overhead, just drop it into an `eval` block. -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply]
Re: •Re: Re: Say no to ref $thing eq "Expected::Type" by rir (Vicar) on Oct 29, 2002 at 19:23 UTC
•Re: Re: •Re: Re: Say no to ref $thing eq "Expected::Type" by merlyn (Sage) on Oct 29, 2002 at 19:34 UTC
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