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

Hi,

I need to map exceptions to error-codes (which will be embedded in a client-response).

Most of the exceptions are instances of Exception::Class-subclasses and the mapping is based on the class-name.

I curently do something like this:

my $rc;

given($ex) {
 when($ex->isa("MyException::Class1")) { $rc = 1; }
 when($ex->isa("MyException::Class2")) { $rc = 2; }
 default { $rc = 3 }
}

# and now pass on $rc to a template

[download]
And I find that not very pleasing.

Is there a better way to do this?

Or can I do an isa-check via ~~

Many thanks!

Replies are listed 'Best First'.
Re: switch question
by roboticus (Chancellor) on Jan 06, 2011 at 23:46 UTC

    morgon:

    How about having a simple hash table then? Something like:

    my %XMap = (
    'MyException::Class1'=>1,
    'MyException::Class2'=>2,
    ...
);

sub errorcode {
   my $ex = shift;
   my $type = ref $ex;
   return $XMap{$type} if exists $XMap{$type}
   return 3; # default
}

    [download]

    ...roboticus

    When your only tool is a hammer, all problems look like your thumb.

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[d/l]
Re: switch question
by lamprecht (Friar) on Jan 06, 2011 at 22:24 UTC

    Maybe your exception classes should implement errorcode()?

    Cheers Christoph 
    BEGIN{
    sub Exception::Class::Base::errorcode{
        my %def = shift->_defaults;
        return $def{errorcode} ;
    }

    sub Exception::Class::Base::_defaults{
        return (errorcode => 3);
    }
}

use Exception::Class (
      'MyException' => {defaults => {errorcode => 2}
                        },

      'AnotherException' => { isa => 'MyException' },

      'YetAnotherException' => {
          isa         => 'AnotherException',
          defaults    => {errorcode => 5},
      },

  );

eval { YetAnotherException->throw( error => 'I feel funny.' ) };

my $e;

if ( $e = Exception::Class->caught()){
    warn $e->error, "\n";
    warn $e->errorcode , "\n";
}

    [download]
    update: example added
[reply]
[d/l]
[select]
      Maybe your exception classes should implement errorcode()?
      I don't want to do that.

      I use this exceptions in other places as well where this mapping is irrelevant (or maybe I also need a mapping but a different one) and that in this particular case they are used to generate a return-code is not the concern of the exception-class.

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