Bio::Root::Root(3) User Contributed Perl Documentation Bio::Root::Root(3)NAMEBio::Root::Root - Hash-based implementation of Bio::Root::RootI
SYNOPSIS
# Any Bioperl-compliant object is a RootI compliant object
# Here's how to throw and catch an exception using the eval-based syntax.
$obj->throw("This is an exception");
eval {
$obj->throw("This is catching an exception");
};
if( $@ ) {
print "Caught exception";
} else {
print "no exception";
}
# Alternatively, using the new typed exception syntax in the throw() call:
$obj->throw( -class => 'Bio::Root::BadParameter',
-text => "Can not open file $file",
-value => $file );
# Want to see debug() outputs for this object
my $obj = Bio::Object->new(-verbose=>1);
my $obj = Bio::Object->new(%args);
$obj->verbose(2);
# Print debug messages which honour current verbosity setting
$obj->debug("Boring output only to be seen if verbose > 0\n");
DESCRIPTION
This is a hashref-based implementation of the Bio::Root::RootI
interface. Most Bioperl objects should inherit from this.
See the documentation for Bio::Root::RootI for most of the methods
implemented by this module. Only overridden methods are described
here.
Throwing Exceptions
One of the functionalities that Bio::Root::RootI provides is the
ability to throw() exceptions with pretty stack traces. Bio::Root::Root
enhances this with the ability to use Error (available from CPAN) if it
has also been installed.
If Error has been installed, throw() will use it. This causes an
Error.pm-derived object to be thrown. This can be caught within a
"catch{}" block, from wich you can extract useful bits of information.
If Error is not installed, it will use the Bio::Root::RootI-based
exception throwing facilty.
Typed Exception Syntax
The typed exception syntax of throw() has the advantage of plainly
indicating the nature of the trouble, since the name of the class is
included in the title of the exception output.
To take advantage of this capability, you must specify arguments as
named parameters in the throw() call. Here are the parameters:
-class
name of the class of the exception. This should be one of the
classes defined in Bio::Root::Exception, or a custom error of yours
that extends one of the exceptions defined in Bio::Root::Exception.
-text
a sensible message for the exception
-value
the value causing the exception or $!, if appropriate.
Note that Bio::Root::Exception does not need to be imported into your
module (or script) namespace in order to throw exceptions via
Bio::Root::Root::throw(), since Bio::Root::Root imports it.
Try-Catch-Finally Support
In addition to using an eval{} block to handle exceptions, you can also
use a try-catch-finally block structure if Error has been installed in
your system (available from CPAN). See the documentation for Error for
more details.
Here's an example. See the Bio::Root::Exception module for other pre-
defined exception types:
try {
open( IN, $file) || $obj->throw( -class => 'Bio::Root::FileOpenException',
-text => "Cannot open file $file for reading",
-value => $!);
}
catch Bio::Root::BadParameter with {
my $err = shift; # get the Error object
# Perform specific exception handling code for the FileOpenException
}
catch Bio::Root::Exception with {
my $err = shift; # get the Error object
# Perform general exception handling code for any Bioperl exception.
}
otherwise {
# A catch-all for any other type of exception
}
finally {
# Any code that you want to execute regardless of whether or not
# an exception occurred.
};
# the ending semicolon is essential!
FEEDBACK
Mailing Lists
User feedback is an integral part of the evolution of this and other
Bioperl modules. Send your comments and suggestions preferably to one
of the Bioperl mailing lists.
Your participation is much appreciated.
bioperl-l@bioperl.org - General discussion
http://bioperl.org/wiki/Mailing_lists - About the mailing lists
Support
Please direct usage questions or support issues to the mailing list:
bioperl-l@bioperl.org
rather than to the module maintainer directly. Many experienced and
reponsive experts will be able look at the problem and quickly address
it. Please include a thorough description of the problem with code and
data examples if at all possible.
Reporting Bugs
Report bugs to the Bioperl bug tracking system to help us keep track
the bugs and their resolution. Bug reports can be submitted via the
web:
http://bugzilla.open-bio.org/
AUTHOR
Functions originally from Steve Chervitz. Refactored by Ewan Birney.
Re-refactored by Lincoln Stein.
APPENDIX
The rest of the documentation details each of the object methods.
Internal methods are usually preceded with a _
new
Purpose : generic instantiation function can be overridden if
special needs of a module cannot be done in _initialize
verbose
Title : verbose
Usage : $self->verbose(1)
Function: Sets verbose level for how ->warn behaves
-1 = no warning
0 = standard, small warning
1 = warning with stack trace
2 = warning becomes throw
Returns : The current verbosity setting (integer between -1 to 2)
Args : -1,0,1 or 2
throw
Title : throw
Usage : $obj->throw("throwing exception message");
or
$obj->throw( -class => 'Bio::Root::Exception',
-text => "throwing exception message",
-value => $bad_value );
Function: Throws an exception, which, if not caught with an eval or
a try block will provide a nice stack trace to STDERR
with the message.
If Error.pm is installed, and if a -class parameter is
provided, Error::throw will be used, throwing an error
of the type specified by -class.
If Error.pm is installed and no -class parameter is provided
(i.e., a simple string is given), A Bio::Root::Exception
is thrown.
Returns : n/a
Args : A string giving a descriptive error message, optional
Named parameters:
'-class' a string for the name of a class that derives
from Error.pm, such as any of the exceptions
defined in Bio::Root::Exception.
Default class: Bio::Root::Exception
'-text' a string giving a descriptive error message
'-value' the value causing the exception, or $! (optional)
Thus, if only a string argument is given, and Error.pm is available,
this is equivalent to the arguments:
-text => "message",
-class => Bio::Root::Exception
Comments : If Error.pm is installed, and you don't want to use it
for some reason, you can block the use of Error.pm by
Bio::Root::Root::throw() by defining a scalar named
$main::DONT_USE_ERROR (define it in your main script
and you don't need the main:: part) and setting it to
a true value; you must do this within a BEGIN subroutine.
debug
Title : debug
Usage : $obj->debug("This is debugging output");
Function: Prints a debugging message when verbose is > 0
Returns : none
Args : message string(s) to print to STDERR
_load_module
Title : _load_module
Usage : $self->_load_module("Bio::SeqIO::genbank");
Function: Loads up (like use) the specified module at run time on demand.
Example :
Returns : TRUE on success. Throws an exception upon failure.
Args : The module to load (_without_ the trailing .pm).
perl v5.14.1 2011-07-22 Bio::Root::Root(3)
