rovf has asked for the wisdom of the Perl Monks concerning the following question:
Hello Monks,
I would like to use Attribute::Default from CPAN in order to define default arguments for subs in a easily readable way. Here is a simple example which works:
This prints abc xyz, followed by a line saying END. Things stop to work, however, when I use Attribute::Default in a package which itself uses the Exporter; or maybe I just may some silly mistake. Here is the first thing I tried:use strict; use warnings; use base 'Attribute::Default'; sub f : Default(undef,"xyz") { print("@_\nEND\n"); } f('abc'); # 2nd argument defaults to xyz
This will be called in the following way:# This is file Co.pm package Co; use strict; use warnings; use base qw(Exporter Attribute::Default); our @EXPORT_OK=qw(f); sub f : Default(undef,"xyz") { print("@_\nEND\n"); } 1;
Executing this will output just abc followed by END; i.e. the default argument is not used.# This is file cotest.pl use warnings; use strict; use Co qw(f); f('abc');
It gets even more bizarre when I handle @ISA by myself instead of letting use base doint it:
I call this as usual,# This is file Co1.pm package Co1; use strict; use warnings; use Exporter; use Attribute::Default; our @ISA=qw(Exporter Attribute::Default); our @EXPORT_OK=qw(f); sub f : Default(undef,"xyz") { print("@_\nEND\n"); } 1;
but now I get the error message:# This is file cotest1.pl use warnings; use strict; use Co qw(f); f('abc');
Well, I guess there is a reason why the perldoc to Attribute::Default says that you need do use base '...' to access it. Anyway, as a last resort I tried to combine the two approaches:Invalid CODE attribute: Default(undef,"xyz") at Co1.pm
The program for calling it is, not surprisingly:# This is Co2.pm package Co2; use strict; use warnings; use Exporter; our @ISA=qw(Exporter); use base qw(Attribute::Default); our @EXPORT_OK=qw(f); sub f : Default(undef,"xyz") { print("@_\nEND\n"); } 1;
Now I get the error message:use warnings; use strict; use Co2 qw(f); f('abc');
What is going wrong here?Can't locate object method "_ATTR_CODE_Default" via package "Co2"
--
Ronald Fischer <ynnor@mm.st>
Ronald Fischer <ynnor@mm.st>
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