oracular (3) Badger::Base.3pm.gz
NAME
Badger::Base - base class module
SYNOPSIS
# define a new object class derived from Badger::Base
package Your::Badger::Module;
use base 'Badger::Base';
sub init {
my ($self, $config) = @_;
# $config is a hash of named parameters
# - let's assume 'name' is mandatory
$self->{ name } = $config->{ name }
|| return $self->error('no name specified');
# save the rest of the config for later
$self->{ config } = $config;
# return $self to indicate success
return $self;
}
# ...any other methods follow....
# now use it
use Your::Badger::Module
my $object = Your::Badger::Module->new( name => 'Brian' );
DESCRIPTION
This module implements a base class object from which most of the other "Badger" modules are derived. It
implements a number of methods to aid in object creation, configuration, error handling and debugging.
You can use it as a base class for your own modules to inherit the methods that it provides.
package Your::Badger::Module;
use base 'Badger::Base';
You can inherit the default new() constructor method and define your own init() method to initialise
objects.
sub init {
my ($self, $config)
# $config is a hash of named parameters
# - let's assume 'name' is mandatory
$self->{ name } = $config->{ name }
|| return $self->error('no name specified');
# save the rest of the config in case any other
# methods want to use it later
$self->{ config } = $config;
# return $self to indicate success
return $self;
}
You can then use your module and instantiate objects. The new() method accepts a list or reference to a
hash array of named parameters.
use Your::Badger::Module;
# list of named parameters
my $object = Your::Badger::Module->new( name => 'Brian' );
# hash ref of name parameters
my $object = Your::Badger::Module->new({ name => 'Brian' });
"Badger::Base" provides a number of other methods that are generally suitable for all (or most) objects
to inherit. These include methods for error reporting, debugging and raising warnings.
METHODS
new(\%config)
This is a general purpose constructor method. It accepts either a reference to a hash array of named
parameters or a list of named parameters which are then folded into a hash reference.
# hash reference of named params
my $object = Your::Badger::Module->new({
arg1 => 'value1',
arg2 => 'value2',
...etc...
});
# list of named params
my $object = Your::Badger::Module->new(
arg1 => 'value1',
arg2 => 'value2',
...etc...
);
The constructor creates a new object by blessing a hash reference and then calling the "init()" method. A
reference to the hash array of named parameters is passed as a single argument. In most cases you should
be able to re-use the existing new() method and define your own init() method to initialise the object.
The "new()" method returns whatever the init() method returns. This will normally be the $self object
reference, but your own init() methods are free to return whatever they like. However, it must be a true
value of some kind or the new() method will throw an error indicating that the init() method failed.
init(\%config)
This initialisation method is called by the "new()" constructor method. This is the method that you'll
normally want to redefine when you create a subclass of "Badger::Base".
The "init()" method is passed a reference to a hash array of named configuration parameters. The method
may perform any configuration or initialisation processes and should generally return the $self reference
to indicate success.
sub init {
my ($self, $config) = @_;
# set the 'answer' parameter or default to 42
$self->{ answer } = $config->{ answer } || 42;
return $self;
}
The "init()" method can return any true value which will then be sent back as the return value from
new(). In most cases you'll want to return the $self object reference, but the possibility exists of
returning other values instead (e.g. to implement singletons, prototypes, or some other clever object
trickery).
If something goes wrong in the "init()" method then you should call the error() method (or error_msg())
to throw an error.
sub init {
my ($self, $config) = @_;
# set the 'answer' parameter or report error
$self->{ answer } = $config->{ answer }
|| return $self->error('no answer supplied');
return $self;
}
The only function of the default init() method in "Badger::Base" is to save a reference to the $config
hash array in "$self->{ config }". If you use the default init() method, or add an equivalent line to
your own init() method, then you can defer inspection of the configuration parameters until later. For
example, you might have a method which does something like this:
our $DATE_FORMAT = '%Y-%d-%b';
sub date_format {
my $self = shift;
return @_
? ($self->{ date_format } = shift) # set from argument
: $self->{ date_format } # get from self...
||= $self->{ config }->{ date_format } # ...or config...
|| $DATE_FORMAT; # ...or pkg var
}
This allows you to use "$self->{date_format}" as a working copy of the value while keeping the original
configuration value (if any) intact in "$self->{config}->{date_format}". The above method will set the
value if you pass an argument and return the current value if you don't. If no current value is defined
then it defaults to the value in the config hash or the $DATE_FORMAT package variable. Now any other
methods that require access to a date format need only call to the "date_format()" method to have it Do
The Right Thing.
The benefit here is that you don't have to waste time (and memory) in the init() method copying the
"date_format" parameter from $config into $self. That doesn't mean that it's always the right thing to
do, but it can be useful for configuration options that are infrequently used.
The on_error() and on_warn() methods follow this protocol. They look for an "ON_ERROR" or "ON_WARN" item
in $self or an "on_error" or "on_warn" parameter in "$self->{config}". If you want to define "on_error"
and/or "on_warn" handlers as configuration parameters then you'll need to either copy the $config
reference into "$self->{config}" or copy the individual items into "$self->{ON_ERROR}" and/or
"$self->{ON_WARN}", respectively.
# either copy the config...
sub init {
my ($self, $config) = @_;
$self->{ config } = $config;
# ...more code...
return $self;
}
# ...or the individual items
sub init {
my ($self, $config) = @_;
# no need to check if either of these are defined because the
# on_warn() and on_error() methods will Do The Right Thing.
$self->{ ON_WARN } = $config->{ on_warn };
$self->{ ON_ERROR } = $config->{ on_error };
# ...more code...
return $self;
}
With either of the above in place, you can then define "on_warn" and "on_error" handlers and expect them
to work when the error() and warn() methods are called.
my $object = Your::Badger::Module->new(
on_warn => \&my_warn,
on_error => \&my_error,
);
$object->warn("Rebel Alliance engaging"); # calls my_warn()
$object->error("Exhaust port unshielded!"); # calls my_error()
warn($message)
A method to raise a warning. The default behaviour is to forward all arguments to Perl's "warn"
function. However, you can install your own warning handlers on a per-class or per-object basis using
the on_warn() method or by setting a $ON_WARN package variable in your module. See on_warn() for further
details.
$object->warn("Careful with that axe, Eugene!");
on_warn($handler, $another_handler, ...)
This method allows you to install one or more callback handlers which are called whenever a warning is
raised via the warn() method. Multiple handlers can be installed and will be called in turn whenever an
error occurs. The warning message is passed as an argument to the handlers.
For example, if you wanted to forward warning messages to your favourite logging tool, you might do
something like this:
my $log = My::Fave::Log::Tool->new(%log_config);
$object->on_warn(
sub {
my $message = shift;
$log->warning("$message);
return $message;
}
);
The value returned from the callback is forwarded to the next handler (if there is one). If a callback
returns a false value or an empty list then the remaining handlers will not be called.
The default behaviour of the "on_warn()" method is to replace any existing warning handlers with the new
one(s) specified. You can prefix the handler(s) with 'before' or 'after' to add them to the existing
list of handlers. e.g.
$object->on_warn( before => \&one, \&two );
$object->on_warn( after => \&one, \&two );
The on_warn() method returns a reference to the list, so you can also monkey about with it directly if
you want the handler(s) to go somewhere else.
my $handlers = $object->on_warn;
shift(@$handlers, \&one); # add before existing handlers
push(@$handlers, \&two); # add after existing handlers
You can also specify a method name as a warning handler. For example, if you want to automatically
upgrade all warnings to errors for a particular object, you can write this:
$object->on_warn('error'); # calls $object->error() on warnings
You can also specify 'warn' as a handler which will call Perl's "warn()" function. This is the default
value. To explicitly disable any handlers, you can use a value of 0.
$object->on_warn('warn'); # raise warning - the default action
$object->on_warn(0); # no warnings
These values can be imported from Badger::Constants as the "WARN" and "NONE" constants.
use Badger::Constants 'WARN NONE';
$object->on_warn(WARN); # raise warning - the default action
$object->on_warn(NONE); # no warnings
The on_warn() method works equally well as a class method. In this case it sets the $ON_WARN package
variable for the class. This acts as the default handler list for any objects of that class that don't
explicitly define their own warning handlers.
Your::Badger::Module->on_warn(\&handler_sub);
If you prefer you can define this using the $ON_WARN package variable. This will then be used as the
default for all objects of this class.
package Your::Badger::Module;
use base 'Badger::Base';
our $ON_WARN = \&handler_sub;
Multiple values should be defined using a list reference. Method names and the special "warn" flag can
also be included.
our $ON_WARN = [ \&this_code_first, 'this_method_next', 'warn' ]
error($message)
The "error()" method is used for error reporting. When an object method fails for some reason, it calls
the "error()" method passing an argument denoting the problem that occurred. This causes an exception
object to be created (see Badger::Exception) and thrown via "throw()". In this case the "error()" method
will never return.
sub engage {
my $self = shift;
return $self->error('warp drive offline');
}
Multiple arguments can be passed to the "error()" method. They are concatenated into a single string.
sub engage {
my $self = shift;
return $self->error(
'warp drive ',
$self->{ engine_no },
' is offline'
);
}
The error method can also be called without arguments to return the error message previously thrown by a
call to "error()". In this case it performs exactly the same function as the reason() method.
eval { $enterprise->engage }
|| warn "Could not engage: ", $enterprise->error;
The fact that the "error()" method can be called without arguments allows you to write things like this:
# doesn't throw anything if list is empty
$self->error(@list_of_errors);
An existing exception object can also be passed as a single argument to the error method. In this case,
the exception object is re-thrown unmodified.
sub save_the_world {
eval { $self->world_peace };
if ($@) {
$self->call_international_rescue($@); # call Thunderbirds
return $self->error($@); # re-throw error
};
}
ASIDE: You may have noticed in these examples that I'm using the "return" keyword when raising an error.
For example:
return $self->error('warp drive offline');
The "error()" method doesn't return when you call it with arguments so the "return" keyword has no effect
whatsoever. However, I like to put it there to give a clear indication of what my intentions are at that
point. It also means that the code will continue to return even if a subclass should "accidentally"
define a different error() method that doesn't throw an error (don't laugh - it happens). It's also
useful when used in conjunction with syntax highlighting to see at a glance where the potential exit
points from a method are (assuming you make "return" bright red or something obvious like I do).
The "error()" method can also be called as a class method. In this case, it updates and retrieves the
$ERROR package variable in the package of the subclass module. This can be used to raise and examine
errors thrown by class methods.
# calling package error() method
my $object = eval { Your::Badger::Module->new() }
|| warn "Could not create badger module: ",
Your::Badger::Module->error();
# accessing $ERROR package variable
my $object = eval { Your::Badger::Module->new() }
|| warn 'Could not create badger module: ",
$Your::Badger::Module::ERROR;
on_error($handler, $another_handler, ...)
This method is similar to on_warn() in allowing you to install a callback handler which is called
whenever an error is raised via the error() method (or the error_msg() wrapper).
$world->on_error(
sub {
my $message = shift;
Thunderbirds->call({
priority => IR_PRIORITY_HIGH,
message => $message,
});
return $message; # forward message to next handler
}
);
The value returned from the callback is forwarded to the next handler. If a callback returns a false
value or an empty list then the remaining handlers will not be called. However, the error will still be
raised regardless of what any of the handlers do or return.
decline($reason, $more_reasons, ...)
The "decline()" method is used to indicate that a method failed but without raising an error. It is
typically used for methods that are asked to fetch a resource (e.g. a record in a database, file in a
filesystem, etc.) that may not exist. In the case where it isn't considered an error if the requested
resource is missing then the method can call the decline() method. It works like error() in that it
stores the message internally for later inspection via reason(). But instead of throwing the message as
an exception, it simply returns "undef"
sub forage {
my ($self, $name) = @_;
# hard error if database isn't connected
my $db = $self->{ database }
|| return $self->error('no database')
if ($thing = $db->fetch_thing($name)) {
# return true value on success
return $thing;
}
else {
# soft decline if not found
return $self->decline("not found: $name")
}
}
Like error(), the decline() method can be called without arguments to return the most recent decline
message, although it's probably better to use reason() which is designed specifically for that purpose.
The decline() method can also be called as a class method as well as an object method, as per error().
declined()
Returns the values of the internal flag which indicates if an object declined by calling the decline()
method. This is set to 1 whenever the decline() method is called and cleared back to 0 whenever the
error() method is called.
my $result = eval { $forager->fetch('nuts') };
if ($result) {
print "result: $result\n";
}
elsif ($forager->declined) {
print "declined: ", $forager->reason, "\n";
}
else {
print "error: ", $forager->reason, "\n";
}
reason()
Returns the message generated by the most recent call to error() or decline() (or any of the wrapper
methods like error_msg() and decline_msg()).
$forager->forage('nuts and berries')
|| die $forager->reason;
message($type, @args)
This method generates a message using a pre-defined format. Message formats should be defined in a
$MESSAGES package variable in the object's package or one of its base classes.
# base class
package Badger::Example::One
use base 'Badger::Base';
our $MESSAGES = {
hai => 'Hello %s',
};
# subclass
package Badger::Example::Two;
use base 'Badger::Example::One';
our $MESSAGES = {
bye => 'Goodbye %s',
};
# using the classes
package main;
my $two = Badger::Example::Two->new();
$two->message( hai => 'World' ); # Hello World
$two->message( bye => 'World' ); # Goodbye World
The $two object can use message formats defined in its own package ("Badger::Example::Two") and also
those of its base class ("Badger::Example::One").
The messages are formatted using the xprintf() function in Badger::Utils. This is a thin wrapper around
the built-in "sprintf()" function with some additional formatting controls to simplify the process of
using positional arguments.
Messages are used internally by the error_msg() and decline_msg() methods for generating error messages,
but you can use them for any kind of simple message generation.
There are a number of benefits to defining messages in a central repository like this.
First, it makes it easy to reuse the same message format in different places. Also known as the "DRY"
principle - Don't Repeat Yourself.
Second, it allows you to put all your messages in one place instead of dotting them all over your code.
The benefit here is a clearer separation of concerns between the underlying logic of your application and
the presentational aspects.
The third benefit comes as a result of this clear separation - it becomes trivially easy to change the
messages generated by your application because they're all defined in one place (possibly in several
different modules if that's how you choose to break it down, but at least they're in one place in each of
those modules). Possible applications of this include: localising an application to different spoken
languages; generating messages in colour (as the Badger::Debug and Badger::Test modules do); or
formatting messages as HTML.
warn_msg($message, @args)
This is a wrapper around the warn() and message() methods. The first argument defines a message format.
The remaining arguments are then applied to that format via the message() method. The resulting output
is then forwarded to the warn() method.
our $NAME = 'Badger';
our $MESSAGES = {
using_default => "Using default value for %s: %s",
};
sub init {
my ($self, $config) = @_;
if ($config->{ name }) {
$self->{ name } = $config->{ name };
}
else {
$self->warn_msg( using_default => name => $NAME );
$self->{ name } = $NAME;
}
return $self;
}
If a "name" isn't provided as a configuration parameter then the default $NAME will be used and the
following warning will be generated:
Using default value for name: Badger
error_msg($message, @args)
This is a wrapper around the error() and message() methods, similar to warn_msg().
package Your::Zoo;
use base 'Badger::Base';
our $MESSAGES = {
not_found => "I can't find the %s you asked for: %s",
}
sub animal {
my ($self, $name) = @_;
return $self->fetch_an_animal($name)
|| $self->error_msg( missing => animal => $name );
}
Calling the "animal()" method on this object with an animal that can't be found, like this:
$zoo->animal('Badgerpotamus');
Will generate an error message like this:
your.zoo error - I can't find the animal you asked for: Badgerpotamus
decline_msg($message, @args)
This is a wrapper around the decline() and message() methods, similar to warn_msg() and error_msg().
our $MESSAGES = {
not_found => 'No %s found in the forest',
};
sub forage {
my ($self, $name) = @_;
return $self->database->fetch_item($name)
|| $self->decline_msg( not_found => $name );
}
The reason() method can be used to return the message generated.
my $food = $forager->forage('nuts')
|| warn $forager->reason; # No nuts found in the forest
fatal_msg($message, @args)
This is a wrapper around the fatal() and message() methods, similar to error_msg() and co.
throw($type, $info, %more_info)
This method throws an exception by calling "die()". It can be called with one argument, which can either
be a Badger::Exception object (or subclass), or an error message which is upgraded to an exception object
(which makes it behave exactly the same as error()).
# error message - same thing as error()
$object->throw('an error has occurred');
# exception object
$e = Badger::Exception->new(
type => 'engine',
info => 'warp drive offline'
);
$object->throw($e);
In the first case, the exception() and throws() methods will be called to determine the exception class
(Badger::Exception by default) and type for the exception, respectively.
The method can also be called with two arguments. The first defines the exception "type", the second the
error message.
$object->throw( engine => 'warp drive offline' );
The second argument can also be another exception object. If the exception has the same type as the
first argument then it is re-thrown unchanged.
$e = Badger::Exception->new(
type => 'engine',
info => 'warp drive offline'
);
$object->throw( engine => $e ) };
In the example above, the $e exception already has a type of "engine" and so is thrown without change.
If the exception types don't match, or if the exception isn't the right kind of exception object that
we're expecting (as reported by exception()) then a new exception is thrown with the old one attached via
the "info" field.
$object->throw( propulsion => $e );
Here a new "propulsion" exception is thrown, with the previous "engine" exception linked in via the
"info" field. The exception object has type() and info() methods that allow you to inspect its value,
iteratively if necessary. Or you can just print an exception and rely on its overloaded stringification
operator to call the text() method. For the error thrown in the previous example, that would be:
propulsion error - engine error - warp drive offline
throw_msg($type, $message, @args)
This is a wrapper around the throw() and message() methods for throwing custom exceptions using message
formats to generate the error information string. The first argument defines the exception type. The
second is the name of the message format. The remaining arguments are uses to populate the placeholders
in the message format.
our $MESSAGES = {
offline => '%s is offline',
};
sub engage {
my $self = shift;
$self->throw_msg( warp => offline => 'warp drive' )
unless $self->warp_drive_ready;
# make it so
}
# throws the following exception:
warp error - warp drive is offline
try($method, @args)
This method wraps another method call in an "eval" block to catch any exceptions thrown.
my $result = $object->try( fetch => 'answer' ) || 42;
This example is equivalent to:
my $result = eval { $object->fetch('answer') } || 42;
The error thrown can be retrieved using the "reason()" method.
my $result = $object->try( fetch => 'answer' )|| do {
warn "Could not fetch answer: ", $object->reason;
42; # a sensible default
};
If you call the "try()" method without any arguments then it will return a "Badger::Base::Trial" object
as a wafer thin wrapper around the original object. Any methods called on this delegate object will be
forwarded to the original object, wrapped up in an "eval" block to catch any errors thrown.
my $result = $object->try->fetch('answer') ||= do {
...
};
catch($type, $method, @args)
TODO - this method depends on some code in Badger::Exception which I haven't written yet.
throws($type)
You can set the default exception type for throw() by calling the throws() method with an argument,
either as an object method (to affect that object only) or as a class method (to affect all objects that
don't set their own value explicitly). Note that the error() and error_msg() methods call throw()
internally, so changing the exception type will also affect the exceptions thrown by those methods.
# object method
$object->throws('food');
$object->throw('No nuts'); # food error - No nuts
$object->error('No nuts'); # food error - No nuts
# class method
Badger::Example->throws('food');
Badger::Example->throw('No berries'); # food error - No berries
Badger::Example->error('No berries'); # food error - No berries
# all objects of this class now throw food by default
my $badger = Badger::Example->new;
$badger->throw('No cheese'); # food error - No cheese
$badger->error('No cheese'); # food error - No cheese
You can also set this value for an object by passing a "throws" configuration parameter to the new()
constructor method.
my $badger = Badger::Example->new(
throws => 'food',
);
This relies on the default behaviour of the init() method which stores a reference to the original
configuration parameters in "$self->{config}". If you want to use this feature then you should ensure
that any specialised init() method you define does the same thing, or copies the "throws" value from
$config into "$self->{THROWS}".
# example 1: store entire config for later
sub init {
my ($self, $config) = @_;
$self->{ config } = $config;
# do other stuff
return $self;
}
# example 2: extract specific parameter up front
sub init {
my ($self, $config) = @_;
$self->{ THROWS } = $config->{ throws };
# do other stuff
return $self;
}
You can set the default exception type for your own modules that inherit from "Badger::Base" by adding a
$THROWS package variable;
package Badger::Example;
use base 'Badger::Base';
our $THROWS = 'food';
If you don't specify an exception type then one will be generated from the module's class name using the
id() method in Badger::Class.
exception($class)
This method can be used to get or set the exception class for an object. The default value is
Badger::Exception.
use Badger::Example;
use Some::Other::Exception;
Badger::Example->exception('Some::Other::Exception');
# now Badger::Example objects throw Some::Other::Exception
You can set the default exception class for your own modules that inherit from "Badger::Base" by adding a
$EXCEPTION package variable;
package Badger::Example;
use base 'Badger::Base';
use Some::Other::Exception;
our $EXCEPTION = 'Some::Other::Exception';
fatal($info, $more_info, ...)
This method is used internally to raise a fatal error. It bypasses the normal error reporting mechanism
and dies with a stack backtrace by calling "confess()" (see Carp).
The most common reason for a fatal error being raised is calling the message() method (or either of the
error_msg() or decline_msg() wrapper methods) with a message format that doesn't exist. The stack
backtrace will tell you where in your code you're making the call so you can easily find and fix it.
not_implemented($what)
A method of convenience which raises an error indicating that the method isn't implemented
sub example_method {
shift->not_implemented;
}
Calling the "example_method()" would result in an error message similar to this (shown here split across
two lines):
your.badger.module error - example_method() is not implemented
for Your::Badger::Module in /path/to/your/script.pl at line 42
Note that it tells you where the "example_method()" was called from, not where the method is defined.
The "not_implemented()" method is typically used in methods defined in a base classes that subclasses are
expected to re-define (a.k.a. pure virtual methods or abstract methods).
You can pass an argument to be more specific about what it is that isn't implemented.
sub example_method {
shift->not_implemented('in base class');
}
The argument is added to the generated error message following the method name. A single space is also
added to separate them.
your.badger.module error - example_method() is not implemented in
base class for Your::Badger::Module in ...etc...
todo($what)
A method of convenience useful during developing to indicate that a method isn't implemented yet. It
raises an error stating that the method is still TODO.
sub not_yet_working {
shift->todo;
}
The error message generated looks something like this:
your.badger.module error - not_yet_working() is TODO in
Your::Badger::Module at line 42
You can pass an argument to be more specific about what is still TODO.
sub not_yet_working {
my ($self, $x) = @_;
if (ref $x) {
$self->todo('support for references');
}
else {
# do something
}
}
The error message generated would then be:
your.badger.module error - not_yet_working() support for
references is TODO in Your::Badger::Module at line 42
debug($msg1,$msg2,...)
This method is mixed in from the Badger::Debug module. It provides a simple way of generating debugging
messages which include the source module and line number where the message was generated.
sub example {
my $self = shift;
$self->debug('entered example()');
# ... some code ...
$self->debug('leaving example()');
}
debug_msg($message, @args)
This is a wrapper around the debug() and message() methods, similar to warn_msg(), error_msg() and
friends.
our $MESSAGES = {
here => 'You are in %s',
};
sub example {
my $self = shift;
$self->debug_msg(
here => 'a maze of twisty little passages, all alike'
) if DEBUG;
# ... some code ...
$self->debug_msg(
here => 'boat, floating on a sea of purest green'
) if DEBUG;
}
debug_up($level,$msg1,$msg2,...)
Another debugging method mixed in from Badger::Debug. This is a wrapper around debug() which reports the
file and line number of a caller higher up the call stack. This is typically used when you create your
own debugging methods, as shown in the following example.
sub parse {
my $self = shift;
while (my ($foo, $bar) = $self->get_foo_bar) {
$self->trace($foo, $bar); # report line here
# do something
}
}
sub trace {
my ($self, $foo, $bar) = @_;
$self->debug_up(2, "foo: $foo bar: $bar"); # not here
}
See Badger::Debug for further details.
PACKAGE VARIABLES
The "Badger::Base" module uses a number of package variables to control the default behaviour of the
objects derived from it.
$DEBUG
This flag can be set true to enable debugging in "Badger::Base".
$Badger::Base::DEBUG = 1;
The "Badger::Base" module does not use or define any $DEBUG variable in the subclasses derived from it.
However, you may want to do something similar in your own modules to assist in debugging.
package Your::Badger::Module;
use base 'Badger::Base';
# allow flag to be set before this module is loaded
our $DEBUG = 0 unless defined $DEBUG;
sub gnarly_method {
my ($self, $item) = @_;
$self->debug("gnarly_method($item)\n") if $DEBUG;
# your gnarly code
}
The "Badger::Class" module defines the "debug" method and import hook which will automatically define a
$DEBUG variable for you.
package Your::Badger::Module;
use Badger::Class
base => 'Badger::Base',
debug => 0;
$DECLINED
This package variable is defined in each subclass derived from "Badger::Base". It is a boolean (0/1) flag
used by the error(), decline() and declined() methods. The decline() method sets it to 1 to indicate that
the object declined a request. The error() method clears it back to 0 to indicate that a hard error
occurred. The declined() method simply returns the value.
$ERROR
This package variable is defined in each subclass derived from "Badger::Base". It stores the most recent
error message raised by decline() or error().
$EXCEPTION
This package variable is used to define the name of the class that should be used to instantiate
exception objects. The default value in "Badger::Base" is "Badger::Exception".
Subclasses may define an $EXCEPTION package variable to change this value.
package Your::Badger::Module;
use base 'Badger::Base';
use Your::Exception;
our $EXCEPTION = 'Your::Exception';
Those that don't explicitly define an $EXCEPTION will inherit the value from any of their base classes,
possibly coming all the way back up to the default value in "Badger::Base".
Calling the "exception()" class method with an argument will update the $EXCEPTION package variable in
that class.
# sets $Your::Badger::Module::EXCEPTION
Your::Badger::Module->exception('Your::Exception');
$MESSAGES
This package variable is used to reference a hash array of messages that can be used with the message(),
warn_msg(), error_msg() and decline_msg() methods. The "Badger::Base" module defines a number of messages
that it uses internally.
our $MESSAGES = {
not_found => '%s not found: %s',
not_found_in => '%s not found in %s',
not_implemented => '%s is not implemented %s',
no_component => 'No %s component defined',
bad_method => "Invalid method '%s' called on %s at %s line %s",
invalid => 'Invalid %s specified: %s',
unexpected => 'Invalid %s specified: %s (expected a %s)',
missing_to => 'No %s specified to %s',
missing => 'No %s specified',
todo => '%s is TODO %s',
at_line => '%s at line %s',
at_file_line => '%s in %s at line %s',
};
The message() method searches for $MESSAGES in the current class and those of any base classes. That
means that any objects derived from "Badger::Base" can use these message formats.
package Your::Badger::Module;
use base 'Badger::Base';
sub init {
my ($self, $config) = @_;
$self->{ name } = $config->{ name }
|| $self->error_msg( missing => $name );
return $self;
}
You can define additional $MESSAGES for your own classes.
package Your::Badger::Module;
use base 'Badger::Base';
our $MESSAGES = {
life_jim => "It's %s Jim, but not as we know it",
}
sub bones {
my ($self, $thing)= @_;
$self->warn_msg( life_jim => $thing );
return $self;
}
Calling the "bones()" method like this:
$object->bones('a badger');
will generate a warning like this:
It's a badger Jim, but not as we know it.
$ON_ERROR
This package variable is used to define one or more error handlers that will be invoked whenever the
error() method is called.
The "Badger::Base" module doesn't define any $ON_ERROR package variable by default. The on_error()
method can be called as a class method to set the $ON_ERROR package variable.
Your::Badger::Module->on_error(\&my_handler);
You can also define an $ON_ERROR handler or list of handlers in your module.
package Your::Badger::Module;
use base 'Badger::Base';
# one of the following...
our $ON_ERROR = 'warn'; # call Perl's warn()
our $ON_ERROR = 'method_name';
our $ON_ERROR = \&code_ref;
our $ON_ERROR = [ 'warn', 'method_name', \&code_ref ];
# code refs get message as first argument
sub code_ref {
my $message = shift;
# do something...
}
# methods get implicit $self, then message argument
sub method_name {
my ($self, $message) = @_;
# do something...
}
$ON_WARN
This package variable is used to define one or more error handlers that will be invoked whenever the
warning() method is called. It works in exactly the same way as $ON_ERROR.
$THROWS
This package variable is used to define the default exception type thrown by the throw() method (and
error() and error_msg() which call it indirectly). It can be set by calling the throws() class method.
Your::Badger::Module->throws('food');
You can define $THROWS in your own modules that are derived from "Badger::Base".
package Your::Badger::Module;
use base 'Badger::Base';
our $THROWS = 'food';
If the $THROWS value is not defined in the current class or any of an object's base classes, then the
id() method is used to construct an identifier for the module to use instead.
OBJECT INTERNALS
The "Badger::Base" module uses the following internal object items to store information.
config
The default init() method stores a reference to the hash array of configuration parameters in the
"$self->{config}" slot. If you're using the default init() method then your other methods can use this to
lookup configuration parameters lazily.
If you've defined your own init() method then this item won't exist unless your init() method adds it
explicitly.
DECLINED
The value of the declined flag, as per the $DECLINED package variable.
ERROR
The last error raised, as per the $ERROR package variable.
EXCEPTION
Used to store the class name that should used to instantiate exceptions. Equivalent to the $EXCEPTION
package variable but operating on a per-object basis. Can be inspected or modified by calling the
exception() object method.
ON_ERROR
An internal list of handlers to call when an error is raised. Equivalent to the $ON_ERROR package
variable but operating on a per-object basis. Can be inspected or modified by calling the on_error()
object method.
ON_WARN
An internal list of handlers to call when a warning is raised. Equivalent to the $ON_WARN package
variable but operating on a per-object basis. Can be inspected or modified by calling the on_warn()
object method.
THROWS
Used to store the exception type that the object should throw. Equivalent to the $THROWS package
variable but operating on a per-object basis. Can be inspected or modified by calling the throws()
object method.
AUTHOR
Andy Wardley <http://wardley.org/>
COPYRIGHT
Copyright (C) 1996-2009 Andy Wardley. All Rights Reserved.
This module is free software; you can redistribute it and/or modify it under the same terms as Perl
itself.