Re^2: P248 programming perl

Number 1 is just weird and number 2 doesn't compile.

Huh? 2 compiles perfectly well for me!

# Doggie.pm
package Doggie;

1;

sub new {
  # ignore args
  print "hello from Doggie::new\n";
}
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use strict;
use warnings;
use Doggie;

sub Doggie {
  print "hello from main::Doggie\n";
}

my $objref1 = Doggie::->new(Tail => 'short', Ears => 'long');
my $objref2 = new Doggie:: Tail => 'short', Ears => 'long';

# The following is parsed as Doggie()->new(...)
# my $objref3 = Doggie->new(Tail => 'short', Ears => 'long');

__END__
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hello from Doggie::new
hello from Doggie::new
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Also, in addition to the use that adrianh cited, 1 would be useful in the rare case in which one wants to use a class that has the same name as a subroutine defined in the client package. In such a case, as the OP has already noted, the parser gets confused with 3.

the lowliest monk

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Re^3: P248 programming perl by wackattack (Sexton) on Jul 05, 2005 at 06:06 UTC
wow, 2 questions: 1)Why does the Doggy.pm need the "#1;"? 2)And how did you get your post to collapse like that? P.S. Perlmonks rule! thanks for the help guys.	[reply]
Re^4: P248 programming perl by holli (Abbot) on Jul 05, 2005 at 06:32 UTC
1)Why does the Doggy.pm need the "#1;"? A module needs to end with a true value, `1;` is the standard convention for that. You could also use `"this is false";`. It just has to be true. :) 2)And how did you get your post to collapse like that? Enclose the poste in `<readmore title="foo">text</readmore>` tags Read more... foo (3 Bytes) holli, /regexed monk/	[reply] [d/l] [select]
Re^4: P248 programming perl by tlm (Prior) on Jul 06, 2005 at 01:10 UTC
1)Why does the Doggy.pm need the "#1;"? Just to clarify holli's point, the value of the last statement in the module file to be evaluated must be true. That's why, in `Doggie.pm` the "`1;`" line is not the last line of the file; the subsequent lines consist entirely of subroutine definitions, which are not evaluated. the lowliest monk	[reply]
Re^3: P248 programming perl by wackattack (Sexton) on Jul 05, 2005 at 06:25 UTC
Also in Doggy.pm I tried inserting the code: print "$objref1->{'tail'}\n"; And I couldn't get it to print short. What am I doing wrong? Sorry for all of the noob questions.	[reply]
Re^4: P248 programming perl by tlm (Prior) on Jul 06, 2005 at 01:00 UTC
As I defined it, the Doggie class has practically no API, other than the rather useless `new` method, which ignores its arguments and, despite its name, doesn't even return an object, new or otherwise! So the main thing you did wrong was trying to use a useless class :-) . (I wrote it that way just to illustrate that the code as written compiles and runs without errors or warnings.) But even if `new` had returned an object, then most OO programmers will tell you that it is wrong software-engineering-wise to attempt to access `$objref1->{'tail'}`, because doing so "violates encapsulation", i.e. abuses a knowledge of how an object is implemented (in this case, presumably, as a hashref). In contrast to my Doggie, a well-designed class will provide accessors for those bits of instance data that are accessible to client code. I.e., you would invoke a method such as `$objref1->tail`. BTW, just for the record, the variable name `$objref1` (which I realize follows the example of PP3, p. 248) is somewhat redundant, because all Perl objects are references. the lowliest monk	[reply]