Custom error messages and moose

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

Greetings, I have the following as part of a moose package.

  has 'ip_address' => (
     is => 'ro',
     isa => 'Str',
     lazy => 1,
     builder => 'get_ip_address',

...

  sub get_ip_address {
     my $self = shift;
     my $allclasses_file = $self->allclasses_file;
     my $ip_address;

     if ( $allclasses_file =~ m/_([^_]+$)/ ) {
        $ip_address = $1;
        return  $ip_address;
     }
  }
[download]

This works. However, if the attribute is not correct the error messege is long and unhelpful. How can I make a custom more friendly messege when the ip_address attribute is incorrect?

Neil Watson
watson-wilson.ca

Comment on Custom error messages and moose Download Code

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Re: Custom error messages and moose by remiah (Hermit) on Sep 29, 2012 at 11:57 UTC
Do you show me your error message? if I return undef to isa 'Str' attribute, I will see like this. Attribute (ip_address) does not pass the type constraint because: Validation failed for 'Str' with value undef at reader test::ip_address (defined at 069.pl line 7) line 15 test::ip_address('test=HASH(0x284a2320)') called at 069.pl line 35 Or, Is there some reason you can't die like this ? `sub get_ip_address { my $self = shift; my $allclasses_file = $self->allclasses_file; my $ip_address; if ( $allclasses_file =~ m/_([^_]+$)/ ) { $ip_address = $1; return $ip_address; } else { die "not good ip\n"; } }` [download]	[reply] [d/l]
Re^2: Custom error messages and moose by neilwatson (Priest) on Sep 29, 2012 at 12:09 UTC
There is pretty verbose: Use of uninitialized value $ip in gethostbyaddr at /home/neil/perl5/li +b/perl5/Evolvethinking/Unicorn.pm line 67, <FH> line 1. Attribute (fqhn) does not pass the type constraint because: Validation + failed for 'Str' with value undef at /home/neil/perl5/lib/perl5/x86_ +64-linux-thread-multi/Mouse/Util.pm line 383, <FH> line 1. Mouse::Util::throw_error('Mouse::Meta::Attribute=HASH(0x20342d +0)', 'Attribute (fqhn) does not pass the type constraint because: V.. +.', 'data', undef, 'depth', -1) called at /home/neil/perl5/lib/perl5/ +Evolvethinking/Unicorn.pm line 78 Unicorn::insert_record('Unicorn=HASH(0x20d3308)') called at /h +ome/neil/bin/p1.pl line 30 [download] Yes, I can put a die or warn in the sub but, I'm wondering if there is a more Moose like way. Neil Watson watson-wilson.ca	[reply] [d/l]
Re^3: Custom error messages and moose by remiah (Hermit) on Sep 29, 2012 at 15:21 UTC
If you set Environment variable MOOSE_ERROR_STYLE with export MOOSE_ERROR_STYLE=croak , you can cut confess style backtrace output. There seems to be discussion for error handling of Moose. I have no further experience for this. regards.	[reply]
Re: Custom error messages and moose by tobyink (Canon) on Sep 29, 2012 at 15:00 UTC
Type constraints allow custom error messages. So you could create an "IPAddress" type constraint as a subtype of "Str", and provide an error message for that. See Moose::Util::TypeConstraints. `perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'`	[reply]
Re: Custom error messages and moose by irirgem (Novice) on Sep 29, 2012 at 04:04 UTC
You could always put in a test like `my $ip_address = ""; if ( $allclasses_file =~ m/_([^_]+$)/ ) { $ip_address = $1; unless ($ip_address =~ m/\d+\.\d+\.\d+\.\d+/) { print "Bad ip value $ip_address\n"; } } return $ip_address;` [download] or just change your code to use the '\d+\.\d+\.\d+\.\d+' like this `my $ip_address = ""; if ( $allclasses_file =~ m/_(\d+\.\d+\.\d+\.\d+)$/) { $ip_address = $1; } return $ip_address;` [download]	[reply] [d/l] [select]