X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FMoose%2FCookbook%2FWTF.pod;h=4b07bcdd514bac090d82cca2e1f59bf14a6536d9;hb=9ac00c2b3a0a546b96c5b88f582e199b2f772d3e;hp=0c0ccf25d034f3eae1dfdefa4a7c5cab61df5b22;hpb=e67a0fca94990eac69dc5e8f8f189162f760c7e6;p=gitmo%2FMoose.git diff --git a/lib/Moose/Cookbook/WTF.pod b/lib/Moose/Cookbook/WTF.pod index 0c0ccf2..4b07bcd 100644 --- a/lib/Moose/Cookbook/WTF.pod +++ b/lib/Moose/Cookbook/WTF.pod @@ -7,7 +7,50 @@ Moose::Cookbook::WTF - For when things go wrong with Moose =head1 COMMON PROBLEMS -=head2 Constructors +=head2 Speed + +=head3 Why is my code taking so long to load? + +Moose does have a compile time performance burden, +which it inherits from Class::MOP. If load/compile +time is a concern for your application, Moose may not +be the right tool for you. + +Although, you should note that we are exploring the +use of L to try and reduce this problem, +but nothing is ready yet. + +=head3 Why are my objects taking so long to construct? + +Moose uses a lot of introspection when constructing an +instance, and introspection can be slow. This problem +can be solved by making your class immutable. This can +be done with the following code: + + MyClass->meta->make_immutable(); + +Moose will then memoize a number of meta-level methods +and inline a constructor for you. For more information +on this see the L section below and in the +L. + +=head2 Constructors & Immutability + +=head3 I made my class immutable, but C it is still slow! + +Do you have a custom C method in your class? Moose +will not overwrite your custom C method, you would +probably do better to try and convert this to use the +C method or possibly set C values in +the attribute declaration. + +=head3 I made my class immutable, and now my (before | after | + around) C is not being called? + +Making a I, I or I wrap around the +C method, will actually create a C method within +your class. This will prevent Moose from creating one itself +when you make the class immutable. =head2 Accessors @@ -29,7 +72,7 @@ because of the order in which classes are constructed, Moose would overwrite your custom accessor. You wouldn't want that would you? -=head2 Method Modfiers +=head2 Method Modifiers =head3 How come I can't change C<@_> in a C modifier? @@ -66,17 +109,103 @@ Here is some sample code: return reverse @rv; }; +=head2 Moose and Subroutine Attributes + +=head3 Why don't subroutine attributes I inherited from a superclass work? + +Currently when you subclass a module, this is done at runtime with +the C keyword but attributes are checked at compile time +by Perl. To make attributes work, you must place C in a +C block so that the attribute handlers will be available at +compile time like this: + + BEGIN { extends qw/Foo/ } + +Note that we're talking about Perl's subroutine attributes here, not +Moose attributes: + + sub foo : Bar(27) { ... } + +=head2 Moose and Other Modules + +=head3 Why can't I get Catalyst and Moose to work together? + +See L. + +=head2 Roles + +=head3 How come BUILD is not called for my composed roles? + +BUILD is never called in composed roles. The primary reason is that +roles are B order sensitive. Roles are composed in such a way +that the order of composition does not matter (for information on +the deeper theory of this read the original traits papers here +L). + +Because roles are essentially unordered, it would be impossible to +determine the order in which to execute the BUILD methods. + +As for alternate solutions, there are a couple. + +=over 4 + +=item * + +Using a combination of lazy and default in your attributes to +defer initialization (see the Binary Tree example in the cookbook +for a good example of lazy/default usage +L) + +=item * + +Use attributes triggers, which fire after an attribute it set, to facilitate +initialization. These are described in the L docs and examples can be +found in the test suite. + +=back + +In general, roles should not I initialization, they should either +provide sane defaults or should be documented as needing specific +initialization. One such way to "document" this is to have a separate +attribute initializer which is required for the role. Here is an example of +how to do this: + + package My::Role; + use Moose::Role; + + has 'height' => ( + is => 'rw', + isa => 'Int', + lazy => 1, + default => sub { + my $self = shift; + $self->init_height; + } + ); + + requires 'init_height'; + +In this example, the role will not compose successfully unless the class +provides a C method. + +If none of those solutions work, then it is possible that a role is not +the best tool for the job, and you really should be using classes. Or, at +the very least, you should reduce the amount of functionality in your role +so that it does not require initialization. + =head1 AUTHOR Stevan Little Estevan@iinteractive.comE +Anders Nor Berle Edebolaz@gmail.comE + =head1 COPYRIGHT AND LICENSE -Copyright 2006 by Infinity Interactive, Inc. +Copyright 2006-2009 by Infinity Interactive, Inc. L This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. -=cut \ No newline at end of file +=cut