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 => 'FAST::Bio::Root::BadParameter',
-text => "Can not open file $file",
-value => $file );
# Want to see debug() outputs for this object
my $obj = FAST::Bio::Object->new(-verbose=>1);
my $obj = FAST::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");
# Deep-object copy
my $clone = $obj->clone;DESCRIPTION
This is a hashref-based implementation of the FAST::Bio::Root::RootI interface. Most Bioperl objects should inherit from this.
See the documentation for FAST::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 FAST::Bio::Root::RootI provides is the ability to throw() exceptions with pretty stack traces. FAST::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 FAST::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 FAST::Bio::Root::Exception, or a custom error of yours that extends one of the exceptions defined in FAST::Bio::Root::Exception.
- -text
-
a sensible message for the exception
- -value
-
the value causing the exception or $!, if appropriate.
Note that FAST::Bio::Root::Exception does not need to be imported into your module (or script) namespace in order to throw exceptions via FAST::Bio::Root::Root::throw(), since FAST::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 FAST::Bio::Root::Exception module for other pre-defined exception types:
my $IN;
try {
open $IN, '<', $file or $obj->throw( -class => 'FAST::Bio::Root::FileOpenException',
-text => "Cannot read file '$file'",
-value => $!);
}
catch FAST::Bio::Root::BadParameter with {
my $err = shift; # get the Error object
# Perform specific exception handling code for the FileOpenException
}
catch FAST::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!new
Purpose : generic instantiation function can be overridden if
special needs of a module cannot be done in _initializeclone
Title : clone
Usage : my $clone = $obj->clone();
or
my $clone = $obj->clone( -start => 110 );
Function: Deep recursion copying of any object via Storable dclone()
Returns : A cloned object.
Args : Any named parameters provided will be set on the new object.
Unnamed parameters are ignored.
Comments: Where possible, faster clone methods are used, in order:
Clone::Fast::clone(), Clone::clone(), Storable::dclone. If neither
is present, a pure perl fallback (not very well tested) is used
instead. Storable dclone() cannot clone CODE references. Therefore,
any CODE reference in your original object will remain, but will not
exist in the cloned object. This should not be used for anything
other than cloning of simple objects. Developers of subclasses are
encouraged to override this method with one of their own._dclone
Title : clone
Usage : my $clone = $obj->_dclone($ref);
or
my $clone = $obj->_dclone($ref);
Function: Returns a copy of the object passed to it (a deep clone)
Returns : clone of passed argument
Args : Anything
NOTE : This differs from clone significantly in that it does not clone
self, but the data passed to it. This code may need to be optimized
or overridden as needed.
Comments: This is set in the BEGIN block to take advantage of optimized
cloning methods if Clone or Storable is present, falling back to a
pure perl kludge. May be moved into a set of modules if the need
arises. At the moment, code ref cloning is not supported.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_register_for_cleanup
_unregister_for_cleanup
_cleanup_methods
throw
Title : throw
Usage : $obj->throw("throwing exception message");
or
$obj->throw( -class => 'FAST::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 FAST::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 FAST::Bio::Root::Exception.
Default class: FAST::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 => FAST::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
FAST::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("FAST::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).