examples/root/exceptions3.pl

   1 #!/usr/bin/perl
   2
   3 # This shows that Error objects can be subclassed into more specialized types.
   4 # Bio::Root::FileOpenException is a subclass of  Bio::Root::IOException.
   5 #
   6 # We can write a generic handler to trap any type of IOException
   7 # or we could handle FileOpenExceptions explicitly.
   8 #
   9 # To demo, run this script without any arguments, then try it with an argument
  10 # that doesn't correspond to any file on your system (e.g., foobar).
  11 # Then try running with a valid file name.
  12 #
  13 # This requires Graham Barr's Error.pm module available from CPAN.
  14 #
  15 # Author: Steve Chervitz <sac@bioperl.org>
  16 #
  17
  18 use strict;
  19 use Error qw(:try);
  20 use Bio::Root::Exception;
  21
  22 try {
  23    print "Starting try block.\n";
  24    my $file = shift @ARGV || throw Bio::Root::IOException(-text=>"No file supplied.");
  25
  26    open ( IN, $file) || throw Bio::Root::FileOpenException(-text=>"Can't open file \"$file\"", -value=> $!);
  27
  28    print "Opened file $file\n";
  29
  30 }
  31 catch Bio::Root::IOException with {
  32     # This handler deals with IOException or any of its subclasses.
  33     # We could also write a handler with a `catch Bio::Root::FileOpenException'.
  34     # Such a handler would appear before this one.
  35     my $e = shift;
  36     print "Caught IOException:\n\n$e";
  37 }
  38 finally {
  39      close IN;
  40 };
  41
  42 print "\nDone.\n";