NAME Object::Util - a selection of utility methods that can be called on blessed objects SYNOPSIS use Object::Util; # $foo might be undef, but this should not die if ($foo->$_isa("Bar")) { ...; } DESCRIPTION This module is inspired by Safe::Isa, Object::Tap, and my own OO experiences. It is a hopefully helpful set of methods for working with objects, exposed as lexical coderef variables. Rationale Providing methods as coderefs so that you can do: $object->$_foo(@args) ... is unusual, so probably requires some explanation. Firstly some of these methods are designed to be called on either a blessed object or some kind of unblessed reference or value. Calling a method on an unblessed reference like this will croak: $ref->foo(@args) Ditto calling methods on undef. Coderefs don't suffer from that problem. More importantly though, the aim of this module is that these methods should be available for you to call on *any* object. You can only call `$object->foo(@args)` if $object's class implements a method called `foo`, or inherits from a superclass that does. Coderef methods can be called on any object. This module adopts the $_foo naming convention pioneered by modules such as Safe::Isa. However (unlike Safe::Isa) the coderefs it provides are *true lexical variables* (a.k.a. `my` variables), not package variables (a.k.a. `our` variables). Methods Object construction and manipulation $_new Can be used like `$class->$_new(@args)` to create a new object. Object::Util will use Module::Runtime to *attempt* to load $class if it is not already loaded. $class is expected to provide a method called `new`. Can also be used as `$factory->$_new(@args)` to create a new object, where $factory is a coderef or an object overloading `&{}`. In this case, $_new will simply call `$factory->(@args)` and expect that to return an object. $_clone If the object provides a `clone` method, calls that. Or if the object appears to be Moose- or Mouse-based, clones it using the metaobject protocol. Otherwise takes the naive approach of treating the object as a hashref of attribute values, and creates a new object of the same class. # clone overrides some attributes from the original object my $glenda = $glen->$_clone(name => "Glenda", gender => "f"); That final fallback obviously massively breaks your class' encapsulation, so it should be used sparingly. $_with_traits Calling `$class->$_with_traits(@traits)` will return a new class name that does some extra traits. Should roughly support Moose, Mouse, Moo, and Role::Tiny, though combinations of frameworks (e.g. consuming a Moose role in a Mouse class) will not always work. If $class is actually a (factory) coderef, then this will only *partly* work. Example: my $factory = sub { Foo->new(@_) }; my $instance = $factory->$_with_traits("Bar")->$_new(%args); The object $instance should now be a `Foo` object, and should do the `Bar` role, however if `Bar` defines any *attributes*, then $_new will not have initialized them correctly. This is because of the opacity of the $factory: $_with_traits cannot peek inside it and apply traits to the `Foo` class; instead it needs to build $instance and apply the traits to the already-built object. Therefore any behaviour that `Bar` defines for the constructor will have been ignored. It is sometimes possible to work around this issue using: my $factory = sub { Foo->new(@_) }; my $instance = $factory->$_with_traits("Bar")->$_new(%args); $instance = $instance->$_clone(%args); $_extend Calling `$object->$_extend(\@traits, \%methods)` will add some extra roles and/or methods to an existing object. Either @traits or %methods may be omitted. For example, `$object->$_extends(\@traits)` or `$object->$_extends(\%methods)`. `$object->$_extends()` also works fine, and is a no-op. Like Object::Extend, but with added support for roles. Method call modifiers $_call_if_object `$object->$_call_if_object($method => @args)` works like `$object->$method(@args)`, but if $object is undefined, returns `undef` instead of throwing an exception. $method may be a method name, or a coderef (anonymous method). Same as Safe::Isa. $_try `$object->$_try($method => @args)` works like `$object->$method(@args)`, but if *any exception is thrown* returns `undef` instead. $method may be a method name, or a coderef (anonymous method). $_tap `$object->$_tap($method => @args)` works like `$object->$method(@args)`, but discards the method's return value (indeed it calls the method in void context), and instead returns the object itself, making it useful for chaining. $method may be a method name, or a coderef (anonymous method). Same as Object::Tap, or the `tap` method in Ruby. $_isa `$object->$_isa($class)` works like `isa` as defined in UNIVERSAL, but if $object is undefined, returns false instead of throwing an exception. A shortcut for `$object->$_call_if_method(isa => $class)`. Same as Safe::Isa. $_does `$object->$_does($role)` works like `does` as defined in Moose::Object, but if $object is undefined, returns false instead of throwing an exception. A shortcut for `$object->$_call_if_method(does => $role)`. Same as Safe::Isa. $_DOES `$object->$_DOES($role)` works like `DOES` as defined in UNIVERSAL, but if $object is undefined, returns false instead of throwing an exception. A shortcut for `$object->$_call_if_method(DOES => $role)`. Same as Safe::Isa. $_can `$object->$_can($method)` works like `can` as defined in UNIVERSAL, but if $object is undefined, returns `undef` instead of throwing an exception. There is one other significant deviation from the behaviour of UNIVERSAL's `can` method: $_can also returns true if $method is an unblessed coderef. (The behaviour of $method if it is a blessed object -- particularly in the face of overloading -- can be unintuitive, so is not supported by $_can.) Similar to Safe::Isa, but not quite the same. Object utility methods $_dump Calling `$object->$_dump` returns a Data::Dumper dump of the object, with some useful changes to the default Data::Dumper output. (Same as Data::Dumper::Concise.) If the object provides its own `dump` method, this will be called instead. Implementation Details B::Hooks::Parser is used to inject these methods into your lexical scope, and `Internals::SvREADONLY` (an internal function built into the Perl core) is used to make them read-only, so you can't do: use Object::Util; $_isa = sub { "something else" }; If this module detects that B::Hooks::Parser cannot be used on your version of Perl, or your Perl is too old to have Internals::SvREADONLY, then it has various fallback routes, but the variables it provides may end up as package (`our`) variables, or not be read-only. If the magic works on your version of Perl, but you wish to avoid the magic anyway, you can switch it off: use Object::Util magic => 0; BUGS Please report any bugs to . SEE ALSO Safe::Isa, UNIVERSAL, Object::Tap, MooseX::Clone, Data::Dumper::Concise, Object::Extend. AUTHOR Toby Inkster . COPYRIGHT AND LICENCE This software is copyright (c) 2014 by Toby Inkster. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself. DISCLAIMER OF WARRANTIES THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.