Normal handles as IO::Handle

mscharrer has asked for the wisdom of the Perl Monks concerning the following question:

Hi, I'm writing an OO module which new method can be given a file handle. Internally I like to use IO::File or IO::Handle (I only need read,print,open,close, maybe write), but I like also to support normal Perl file handles.

Now I wrote some code and tests and figured out that normal file handles seems to be already IO::Handle objects, even without 'use IO::Handle'. I'm using Perl 5.8.8. Can anyone tell me when this feature got included into Perl so I know how downward compatible my code will be?

My code should work with *HANDLE, \*HANDLE and *HANDLE{IO} and of course with IO::Handle and derived objects.

use Test::More tests => 4;
use IO::Handle;
use strict;
use warnings;

sub ishandle {
 
    my $h = shift;
    return $h if eval { $h->isa('IO::Handle') };

    return *$h{IO}
      if ref $h eq 'GLOB'
          or ref \$h eq 'GLOB';

    return $h;
}

isa_ok( ishandle( new IO::Handle ), 'IO::Handle' );

isa_ok( ishandle(  *STDIN ),     'IO::Handle' );
isa_ok( ishandle( \*STDIN ),     'IO::Handle' );
isa_ok( ishandle( *STDIN{IO} ),  'IO::Handle' );

__END__
1..4
ok 1 - The object isa IO::Handle
ok 2 - The object isa IO::Handle
ok 3 - The object isa IO::Handle
ok 4 - The object isa IO::Handle
[download]

The function returns a IO::Handle object from all valid inputs. Any comments? Does anyone know a better way to do this?

Support for literal names like 'STDIN' could be added with:

no strict 'refs'
return *$h{IO} if eval { *$h{IO} };
[download]

Comment on Normal handles as IO::Handle Select or Download Code

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Re: Normal handles as IO::Handle by Anonymous Monk on Apr 18, 2008 at 10:41 UTC
`D:\>grep IO::Handle D:\perl\lib\pod\perldel D:\perl\lib\pod\perl5004delta.pod:File handles are now stored internal +ly as type IO::Handle. The D:\perl\lib\pod\perl5004delta.pod:IO::Handle, IO::Seekable, and IO::Fi +le. We suggest, but do not D:\perl\lib\pod\perl5004delta.pod: IO/Handle.pm IO::Handle +extension Perl module D:\perl\lib\pod\perl5004delta.pod: IO::Handle D:\>corelist IO::Handle IO::Handle was first released with perl 5.00307` [download]	[reply] [d/l]
Re^2: Normal handles as IO::Handle by mscharrer (Hermit) on Apr 18, 2008 at 10:47 UTC
Thanks for the information and to show me how to get it.	[reply]
Re: Normal handles as IO::Handle by ikegami (Patriarch) on Apr 18, 2008 at 10:47 UTC
Can anyone tell me when this feature got included into Perl so I know how downward compatible my code will be? Since Perl 5.4 (1997) Now I wrote some code and tests and figured out that normal file handles seems to be already IO::Handle objects, even without 'use IO::Handle'. Yes, but you do need to `use IO::Handle;` to load the methods if you want to use them. `>perl -e"STDOUT->print('');" Can't locate object method "print" via package "IO::Handle" at -e line + 1.` [download]	[reply] [d/l] [select]
Re^2: Normal handles as IO::Handle by mscharrer (Hermit) on Apr 18, 2008 at 10:55 UTC
I knew that. My idea is that I have `use IO::Handle` in my module and the user scripts can just pass *STDIN or any other handle without knowing about IO::Handle.	[reply] [d/l]
Re: Normal handles as IO::Handle by ikegami (Patriarch) on Apr 18, 2008 at 20:53 UTC
You don't even need to convert the argument into a reference. `>perl -MIO::Handle -le"( STDOUT )->print('foo');" foo >perl -MIO::Handle -le"( STDOUT )->print('foo');" foo >perl -MIO::Handle -le"( STDOUT{IO} )->print('foo');" foo >perl -MIO::Handle -le"( \*STDOUT )->print('foo');" foo >perl -MIO::Handle -le"( 'STDOUT' )->print('foo');" foo` [download]	[reply] [d/l]