Moose::Cookbook::WTF - For when things go wrong with Moose
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 Module::Compile to try and reduce this problem, but nothing is ready yet.
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 Constructors section below and in the Moose::Cookbook::FAQ.
new
Do you have a custom new method in your class? Moose will not overwrite your custom new method, you would probably do better to try and convert this to use the BUILD method or possibly set default values in the attribute declaration.
BUILD
default
Making a before, after or around wrap around the new method, will actually create a new method within your class. This will prevent Moose from creating one itself when you make the class immutable.
Accessors are not created implicitly, you must ask Moose to create them for you. My guess is that you have this:
has 'foo' => (isa => 'Bar');
when what you really want to say is:
has 'foo' => (isa => 'Bar', is => 'rw');
The reason this is so, is because it is a perfectly valid use case to not have an accessor. The simplest one is that you want to write your own. If Moose created on automatically, then because of the order in which classes are constructed, Moose would overwrite your custom accessor. You wouldn't want that would you?
@_
before
The before modifier simply is called before the main method. Its return values are simply ignored, and are not passed onto the main method body.
There are a number of reasons for this, but those arguments are too lengthy for this document. Instead, I suggest using an around modifier instead. Here is some sample code:
around
around 'foo' => sub { my $next = shift; my ($self, @args) = @_; # do something silly here to @args $next->($self, reverse(@args)); };
after
As with the before modifier, the after modifier is simply called after the main method. It is passed the original contents of @_ and not the return values of the main method.
Again, the arguments are too lengthy as to why this has to be. And as with before I recommend using an around modifier instead. Here is some sample code:
around 'foo' => sub { my $next = shift; my ($self, @args) = @_; my @rv = $next->($self, @args); # do something silly with the return values return reverse @rv; };
Currently when you subclass a module, this is done at runtime with the extends keyword but attributes are checked at compile time by Perl. To make attributes work, you must place extends in a BEGIN block so that the attribute handlers will be available at compile time like this:
extends
BEGIN
BEGIN { extends qw/Foo/ }
See "Moose and Attributes".
Stevan Little <stevan@iinteractive.com>
Anders Nor Berle <debolaz@gmail.com>
Copyright 2006, 2007 by Infinity Interactive, Inc.
http://www.iinteractive.com
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
To install Moose, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Moose
CPAN shell
perl -MCPAN -e shell install Moose
For more information on module installation, please visit the detailed CPAN module installation guide.