Re: Creating exception classes

[7stud]

use strict;
use warnings;
use 5.012;

use Exception::Class (
    'MyException',

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

    'TimeoutException' => {
        isa => 'CommandException',
        description =>
          'This exception resulted from running the metrics commands'
    },
    'DBException' => {
        isa         => 'MyException',
        description => 'DB returned error'
      }

);

&ThrowMyException();

sub ThrowMyException() {

    eval{ TimeoutException->throw(error=>"This is error due to timeout
+") };
    my $err;

    if ($err = Exception::Class->caught('TimeoutException') ) {
         #print Dumper($err);
         #print "err is of type ".ref($err);
         die $err->description . ": " . $err->error;
    }
    elsif ( $err = Exception::Class->caught("MetricsException") ) {
        #print Dumper($err);
        die $err->error;
    }


}

If you see class names like A::B::C, that means the class is named C and it can be found in the directory A/B/. The A::B:: part is a namespace name to prevent name conflicts, but it also indicates the directory structure where the class is located. When you write A::B::C in your program, perl searches all the directories in @INC for a directory named A that has a subdirectory named B, which contains a file called C.pm.

[tobyink]

"When you write A::B::C in your program, perl searches all the directories in @INC for a directory named A that has a subdirectory named B, which contains a file called C.pm."

No it doesn't. It only does that search if you write use A::B::C, no A::B::C or require A::B::C. Merely mentioning the A::B::C package (for example, to call a constructor) does not force Perl to attempt to load the module.

The following code does not attempt to load "This/File/Does/No/Exist/On/My/Disk.pm"...

use strict;
use warnings;

{
    package This::File::Does::No::Exist::On::My::Disk;
    require Math::BigInt;
    our @ISA = 'Math::BigInt';
}

my $number = This::File::Does::No::Exist::On::My::Disk->new(7);
print $number * 6, "\n";