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Custom error messages and moose

by neilwatson (Deacon)
on Sep 29, 2012 at 00:39 UTC ( #996308=perlquestion: print w/ replies, xml ) Need Help??
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
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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]
Re: Custom error messages and moose
by remiah (Friar) 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]
      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]

        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 (Prior) 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]

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