=head1 NAME
-Moose::Cookbook::FAQ - Frequenty asked questions about Moose
+Moose::Cookbook::FAQ - Frequently asked questions about Moose
=head1 FREQUENTLY ASKED QUESTIONS
+=head2 Module Stability
+
+=head3 Is Moose "production ready"?
+
+Yes. I have several medium-to-large-ish web applications in
+production using Moose, they have been running without
+issue now for well over a year.
+
+At C<$work> we are re-writing our core offering to use Moose,
+so it's continued development is assured.
+
+Several other people on #moose either have apps in production
+which use Moose, or are in the process of deploying sites
+which use Moose.
+
+=head3 Is Moose's API stable?
+
+Yes and No. The external API, the one 90% of users will interact
+with, is B<very stable> and any changes B<will be 100% backwards
+compatible>. The introspection API is I<mostly> stable; I still
+reserve the right to tweak that if needed, but I will do my
+absolute best to maintain backwards compatibility here as well.
+
+=head3 I heard Moose is slow, is this true?
+
+Again, this one is tricky, so Yes I<and> No.
+
+First let me say that I<nothing> in life is free, and that some
+Moose features do cost more than others. It is also the
+policy of Moose to B<only charge you for the features you use>,
+and to do our absolute best to not place any extra burdens on
+the execution of your code for features you are not using. Of
+course using Moose itself does involve some overhead, but it
+is mostly compile time. At this point we do have some options
+available for getting the speed you need.
+
+Currently we have the option of making your classes immutable
+as a means of boosting speed. This will mean a slightly larger compile
+time cost, but the runtime speed increase (especially in object
+construction) is pretty significant. This is not very well
+documented yet, so please ask on the list or on #moose for more
+information.
+
+We are also discussing and experimenting with L<Module::Compile>,
+and the idea of compiling highly optimized C<.pmc> files. In
+addition, we have mapped out some core methods as candidates for
+conversion to XS.
+
+=head3 When will Moose 1.0 be ready?
+
+It is right now, I declared 0.18 to be "ready to use".
+
=head2 Constructors
=head3 How do I write custom constructors with Moose?
use Moose's other features to handle your specific object construction
needs. Here are a few scenarios, and the Moose way to solve them;
-If you need to call initializtion code post instance construction,
+If you need to call initialization code post instance construction,
then use the C<BUILD> method. This feature is taken directly from
-Perl 6. Every C<BUILD> method in your inheritence chain is called
+Perl 6. Every C<BUILD> method in your inheritance chain is called
(in the correct order) immediately after the instance is constructed.
This allows you to ensure that all your superclasses are initialized
properly as well. This is the best approach to take (when possible)
-because it makes subclassing your class much easier.
+because it makes sub classing your class much easier.
If you need to affect the constructor's parameters prior to the
instance actually being constructed, you have a number of options.
version from L<Moose::Object>.
The last approach is to use the standard Perl technique of calling
-the C<SUPER::new> within your own custom version of C<new>. This
-of course brings with it all the issues of the C<around> solution
-along with any issues C<SUPER::> might add as well.
+the C<SUPER::new> within your own custom version of C<new>. This,
+of course, brings with it all the issues of the C<around> solution
+as well as any issues C<SUPER::> might add.
In short, try to use C<BUILD> and coercions, they are your best
bets.
-=head3 How do I make non-Moose constuctors work with Moose?
+=head3 How do I make non-Moose constructors work with Moose?
-Moose provides it's own constructor, but it does it by making all
+Moose provides its own constructor, but it does it by making all
Moose-based classes inherit from L<Moose::Object>. When inheriting
-from a non-Moose class, the inheritence chain to L<Moose::Object>
+from a non-Moose class, the inheritance chain to L<Moose::Object>
is broken. The simplest way to fix this is to simply explicitly
inherit from L<Moose::Object> yourself. However, this does not
always fix the issue of a constructor. Here is a basic example of
package My::HTML::Template;
use Moose;
- # explict inheritence
+ # explicit inheritance
extends 'HTML::Template', 'Moose::Object';
# explicit constructor
);
}
-Of course this only works if both your Moose class, and the
+Of course, this only works if both your Moose class and the
inherited non-Moose class use the same instance type (typically
HASH refs).
Other techniques can be used as well, such as creating the object
using C<Moose::Object::new>, but calling the inherited non-Moose
-class's initializtion methods (if available).
+class's initialization methods (if available).
-It is also entirely possible to just rely on HASH autovivification
-to create the slot's needed for Moose based attributes. Although
-this does somewhat restrict use of construction time attribute
-features.
+It is also entirely possible to just rely on HASH autovivification
+to create the slots needed for Moose based attributes, although this
+does restrict use of construction time attribute features somewhat.
In short, there are several ways to go about this, it is best to
evaluate each case based on the class you wish to extend, and the
Moose will still take advantage of type constraints, triggers, etc.
when creating these methods.
-If you do not like this much typing, and wish it to be a default for
-your class. Please see L<Moose::Policy>, and more specifically the
-L<Moose::Policy::FollowPBP>. This will allow you to write this:
+If you do not like this much typing, and wish it to be a default for
+your class, please see L<Moose::Policy>, and more specifically
+L<Moose::Policy::FollowPBP>. This will allow you to write:
has 'bar' => (
isa => 'Baz',
is => 'rw',
);
-And have Moose create C<get_bar> and C<set_bar> instead of the usual
-C<bar>.
+And have Moose create seperate C<get_bar> and C<set_bar> methods
+instead of a single C<bar> method.
-NOTE: This B<cannot> be set globally in Moose, as this would break
+NOTE: This B<cannot> be set globally in Moose, as that would break
other classes which are built with Moose.
=head3 How can I get Moose to inflate/deflate values in the accessor?
and deflate.
If you only need to inflate, then I suggest using coercions. Here is
-some basic sample code for inflating a L<DateTime> object.
+some basic sample code for inflating a L<DateTime> object:
subtype 'DateTime'
=> as 'Object'
This creates a custom subtype for L<DateTime> objects, then attaches
a coercion to that subtype. The C<timestamp> attribute is then told
-to expect a C<DateTime> type, and to try and coerce it. When a C<Str>
+to expect a C<DateTime> type, and to try to coerce it. When a C<Str>
type is given to the C<timestamp> accessor, it will attempt to
coerce the value into a C<DateTime> object using the code in found
in the C<via> block.
-For a more detailed and complete example of coercions, see the
+For a more comprehensive example of using coercions, see the
L<Moose::Cookbook::Recipe5>.
If you need to deflate your attribute, the current best practice is to
is also outside the scope of this document, but I would be happy to
explain it on #moose or the mailing list.
-=head2 Method Modfiers
+=head2 Method Modifiers
=head3 How can I affect the values in C<@_> using C<before>?
-You can't actually, C<before> only runs before the main method,
-and it cannot easily affect the execution of it. What you want is
+You can't, actually: C<before> only runs before the main method,
+and it cannot easily affect the method's execution. What you want is
an C<around> method.
=head3 Can I use C<before> to stop execution of a method?
Yes, but only if you throw an exception. If this is too drastic a
measure then I suggest using C<around> instead. The C<around> method
-modifier is the only modifier which can actually stop the execution
+modifier is the only modifier which can gracefully prevent execution
of the main method. Here is an example:
around 'baz' => sub {
my $next = shift;
my ($self, %options) = @_;
- if ($options{bar} eq 'foo') {
- $next->($self, %options);
- }
- else {
- return 'bar';
+ unless ($options->{bar} eq 'foo') {
+ return 'bar';
}
+ $next->($self, %options);
};
By choosing not to call the C<$next> method, you can stop the
=head3 How can I have a custom error message for a type constraint?
-Use the C<message> option when building the subtype. Like so:
+Use the C<message> option when building the subtype, like so:
subtype 'NaturalLessThanTen'
=> as 'Natural'
This will be called when a value fails to pass the C<NaturalLessThanTen>
constraint check.
+=head3 Can I turn off type constraint checking?
+
+Not yet, but soon. This option will likely be coming in the next
+release.
+
+=head2 Roles
+
+=head3 How do I get Moose to call BUILD in all my composed roles?
+
+See L<Moose::Cookbook::WTF> and specifically the B<How come BUILD
+is not called for my composed roles?> question in the B<Roles> section.
+
=head1 AUTHOR
Stevan Little E<lt>stevan@iinteractive.comE<gt>
=head1 COPYRIGHT AND LICENSE
-Copyright 2006 by Infinity Interactive, Inc.
+Copyright 2006-2008 by Infinity Interactive, Inc.
L<http://www.iinteractive.com>
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