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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" Moose::Cookbook::Legacy::Debugging_BaseClassReplacement \- Providing an alternate base object class .SH "VERSION" .IX Header "VERSION" version 2.0603 .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 2 \& package MyApp::Base; \& use Moose; \& \& extends \*(AqMoose::Object\*(Aq; \& \& before \*(Aqnew\*(Aq => sub { warn "Making a new " . $_[0] }; \& \& no Moose; \& \& package MyApp::UseMyBase; \& use Moose (); \& use Moose::Exporter; \& \& Moose::Exporter\->setup_import_methods( also => \*(AqMoose\*(Aq ); \& \& sub init_meta { \& shift; \& return Moose\->init_meta( @_, base_class => \*(AqMyApp::Base\*(Aq ); \& } .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" \&\fB\s-1WARNING:\s0 Replacing the base class entirely, as opposed to applying roles to the base class, is strongly discouraged. This recipe is provided solely for reference when encountering older code that does this.\fR .PP A common extension is to provide an alternate base class. One way to do that is to make a \f(CW\*(C`MyApp::Base\*(C'\fR and add \f(CW\*(C`extends\ \*(AqMyApp::Base\*(Aq\*(C'\fR to every class in your application. That's pretty tedious. Instead, you can create a Moose-alike module that sets the base object class to \f(CW\*(C`MyApp::Base\*(C'\fR for you. .PP Then, instead of writing \f(CW\*(C`use\ Moose\*(C'\fR you can write \f(CW\*(C`use\ MyApp::UseMyBase\*(C'\fR. .PP In this particular example, our base class issues some debugging output every time a new object is created, but you can think of some more interesting things to do with your own base class. .PP This uses the magic of Moose::Exporter. When we call \f(CW\*(C`Moose::Exporter\->setup_import_methods( also => \*(AqMoose\*(Aq )\*(C'\fR it builds \&\f(CW\*(C`import\*(C'\fR and \f(CW\*(C`unimport\*(C'\fR methods for you. The \f(CW\*(C`also => \*(AqMoose\*(Aq\*(C'\fR bit says that we want to export everything that Moose does. .PP The \f(CW\*(C`import\*(C'\fR method that gets created will call our \f(CW\*(C`init_meta\*(C'\fR method, passing it \f(CW\*(C`for_caller => $caller\*(C'\fR as its arguments. The \f(CW$caller\fR is set to the class that actually imported us in the first place. .PP See the Moose::Exporter docs for more details on its \s-1API\s0. .SH "NAME" Moose::Cookbook::Extending::Recipe3 \- Providing an alternate base object class .SH "VERSION" .IX Header "VERSION" version 2.0402 .SH "USING MyApp::UseMyBase" .IX Header "USING MyApp::UseMyBase" To actually use our new base class, we simply use \f(CW\*(C`MyApp::UseMyBase\*(C'\fR \&\fIinstead\fR of \f(CW\*(C`Moose\*(C'\fR. We get all the Moose sugar plus our new base class. .PP .Vb 1 \& package Foo; \& \& use MyApp::UseMyBase; \& \& has \*(Aqsize\*(Aq => ( is => \*(Aqrw\*(Aq ); \& \& no MyApp::UseMyBase; .Ve .SH "CONCLUSION" .IX Header "CONCLUSION" This is an awful lot of magic for a simple base class. You will often want to combine a metaclass trait with a base class extension, and that's when this technique is useful. .SH "AUTHOR" .IX Header "AUTHOR" Moose is maintained by the Moose Cabal, along with the help of many contributors. See \*(L"\s-1CABAL\s0\*(R" in Moose and \*(L"\s-1CONTRIBUTORS\s0\*(R" in Moose for details. .SH "COPYRIGHT AND LICENSE" .IX Header "COPYRIGHT AND LICENSE" This software is copyright (c) 2012 by Infinity Interactive, Inc.. .PP This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself. .SH "AUTHOR" .IX Header "AUTHOR" Moose is maintained by the Moose Cabal, along with the help of many contributors. See \*(L"\s-1CABAL\s0\*(R" in Moose and \*(L"\s-1CONTRIBUTORS\s0\*(R" in Moose for details. .SH "COPYRIGHT AND LICENSE" .IX Header "COPYRIGHT AND LICENSE" This software is copyright (c) 2012 by Infinity Interactive, Inc.. .PP This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.