=head1 WHAT IS MOOSE?
Moose is a I<complete> object system for Perl 5. If you've used a
-modern object-oriented language (which Perl 5 definitely isn't),
-you've seen seen that they provide keywords for things like attribute
-declaration, object construction, and inheritance. These keywords are
-part of the language, and you don't care about how they are implemented.
+modern object-oriented language (which Perl 5 definitely isn't), you
+know they provide keywords for attribute declaration, object
+construction, and inheritance. These keywords are part of the
+language, and you don't care how they are implemented.
Moose aims to do the same thing for Perl 5 OO. We can't actually
-create new keywords, but we do offer "sugar" subroutines that look a
-lot like keywords.
+create new keywords, but we do offer "sugar" that looks a lot like
+them. More importantly, with Moose, you I<declaritively define> your
+class, without needing to know about blessed hashrefs, accessor
+methods, and so on.
-Moose tries to get you thinking about the I<logical> structure of your
-classes, rather than the underlying implementation. Your class
-definitions are I<declarative>, focusing on "what" rather than
-"how". With Moose, a class definition should read like a list of very
-concise English sentences.
+Moose lets you focus on the I<logical> structure of your classes, so
+you can focus on "what" rather than "how". With Moose, a class
+definition should read like a list of very concise English sentences.
Moose is built in top of C<Class::MOP>, a meta-object protocol (aka
MOP). Using the MOP, Moose provides complete introspection for all
Moose-using classes. This means you can ask classes about their
attributes, parents, children, methods, etc., all using a well-defined
-API. The MOP abstracts digging about in the Perl symbol table and
-looking at C<@ISA> vars.
+API. The MOP abstracts away tedious digging about in the Perl symbol
+table, looking at C<@ISA> vars, and all the other crufty Perl tricks
+we know and love (?).
-All of this work is based in large part on the Perl 6 object system,
-which in turn draws from CLOS, Smalltalk, and other languages.
+Moose is based in large part on the Perl 6 object system, as well as
+drawing on the best ideas from CLOS, Smalltalk, and many other
+languages.
=head1 WHY MOOSE?
-Moose makes Perl 5 OO simpler, while adding power. It encapsulates all
-the tricks of Perl 5 power users, like symbol table manipulation, in
-high-level declarative APIs which are easy to use, and don't require
-any special knowledge of how Perl works under the hood.
+Moose makes Perl 5 OO both simpler and more powerful. It encapsulates
+all the tricks of Perl 5 power users in high-level declarative APIs
+which are easy to use, and don't require any special knowledge of how
+Perl works under the hood.
Moose makes Perl 5 OO fun, accessible, and powerful. And if you want
-to dig under the hood, Moose lets you do that too, by using and
-extending its introspection API.
+to dig about in the guts, Moose lets you do that too, by using and
+extending its powerful introspection API.
=head1 AN EXAMPLE
}
We'll leave the line-by-line explanation of this code to other
-documentation, but just reading it you can get a sense of what these
-classes are.
+documentation, but you can see how Moose reduces common OO idioms to
+simple declarative constructs.
=head2 Where's the Constructor?
implemented. Simply define a class and you're ready to start creating
objects!
-=head1 MOOSE CONCEPT (VS "OLD SCHOOL" Perl)
+=head1 MOOSE CONCEPTS (VS "OLD SCHOOL" Perl)
-In the past, you may not have though too much about difference between
-packages and classes, attributes and methods, constructors vs methods,
-etc. Part of what the MOP provides is well-defined introspection
-features for each of those things, and in turn Moose provides
-I<distinct> sugar for each of them. Moose also introduces concepts
-that are uncommon (or entirely new) like roles, method modifiers, and
-declarative delegation.
+In the past, you may not have thought too much about the difference
+between packages and classes, attributes and methods, constructors vs
+methods, etc. Part of what the MOP provides is well-defined
+introspection features for each of those things, and in turn Moose
+provides I<distinct> sugar for each of them. Moose also introduces
+concepts that are uncommon (or entirely new) like roles, method
+modifiers, and declarative delegation.
-It is helpful to define each of these concepts the Moose way, and to
-distinguish them from the "old school" Perl 5 OO way.
+Knowing what these concepts mean in Moose-speak, and how they used to
+be done in old school Perl 5 OO is a good way to start learning to use
+Moose.
=head2 Class
When you say "use Moose" in a package, you are defining your package
-as a class. At its most simple, a class will consist of attributes
+as a class. At its simplest, a class will consist simply of attributes
and/or methods. It can also include roles, method modifiers, and more.
-A class I<has> (owns) zero or more B<attributes>.
+A class I<has> zero or more B<attributes>.
A class I<has> zero or more B<methods>.
class inherits from its superclass(es).
A class may I<have> B<method modifiers>. These modifiers can apply to
-its own methods or methods belonging to any of its parents.
+its own methods or methods that are inherited from its ancestors.
A class may I<do> one or more B<roles>.
-A class I<has> a B<constructor> and a B<destructor>, and these are
-automatically provided for you by Moose. The constructor produces
-B<object instances>.
+A class I<has> a B<constructor> and a B<destructor>. These are
+provided for you "for free" by Moose.
+
+The B<constructor> accepts named parameters corresponding to the
+class's attributes and uses them to initialize an B<object instances>.
A class I<has> a B<metaclass>, which in turn has B<meta-attributes>,
B<meta-methods>, and B<meta-roles>. This metaclass I<describes> the
A class is usually analogous to a category of nouns, like "People" or
"Users".
+ package Person;
+
+ use Moose;
+ # now it's a Moose class!
+
=head2 Attribute
An attribute is a property of the class that defines it. It I<always>
-has a name, and it I<may have> a number of other properties.
+has a name, and it I<may have> a number of other defining
+characteristics.
-Its properties may include it a read/write flag, a B<type>, accessor
-method names, B<delegations>, and more.
+These characteristics may include a read/write flag, a B<type>,
+accessor method names, B<delegations>, a default value, and more.
-Attributes I<are not> methods, but by defining them causes various
-methods to be created. Most attributes at least have a reader
-method. Many attributes have things like a writer method, clearer
-method, and predicate method ("has it been set?").
+Attributes I<are not> methods, but defining them causes various
+accessor methods to be created. At a minimum, a normal attribute will
+always have a reader accessor method. Many attributes have things like
+a writer method, clearer method, and predicate method ("has it been
+set?").
+
+An attribute may also define B<delegation>s, which will create
+additional methods based on the delegation specification.
By default, Moose stores attributes in the object instance, which is a
-hashref, I<but this is invisible to a typical Moose-base class
-author>! It is best to think of Moose attributes as "properties" of
-the B<object instance> which are accessed through well-defined
-methods.
+hashref, I<but this is invisible to the author of a Moose-base class>!
+It is best to think of Moose attributes as "properties" of the
+I<opaque> B<object instance>. These properties are accessed through
+well-defined accessor methods.
An attribute is usually analagous to specific feature of something in
the class's category. For example, People have first and last
names. Users have passwords and last login datetimes.
+ has 'first_name' => (
+ is => 'rw',
+ isa => 'Str',
+ );
+
=head2 Method
A method is very straightforward. Any subroutine you define in your
Methods correspond to verbs, and are what your objects can do. For
example, a User can login.
+ sub login { ... }
+
=head2 Roles
A role is something that a class I<does>. For example, a Machine class
might do the Breakable role, and a so could a Bone class. A role is
used to define some concept that cuts across multiple unrelated
-classes, like "breakability".
+classes, like "breakability", or "has a color".
A role I<has> zero or more B<attributes>.
=head2 Method Modifiers
A method modifier is a way of defining an action to be taken when a
-named method is called. For example, you could say "before calling
-C<login()>, call this modifier first". Modifiers come in different
-flavors like "before", "after", "around", and "augment".
+named method is called. Think of it as a hook on the named method. For
+example, you could say "before calling C<login()>, call this modifier
+first". Modifiers come in different flavors like "before", "after",
+"around", and "augment", and you can apply more than one modifier to
+a single method.
Method modifiers are often used as an alternative to overriding a
method in a parent class. They are also used in roles as a way of
modifying methods in the consuming class.
Under the hood, a method modifier is just a plain old Perl subroutine
-that gets called before, after, etc some other method.
+that gets called before or after (or around, etc.) some named method.
before 'login' => sub {
my $self = shift;
Finally, you can define your own types, either as subtypes or entirely
new types, with their own constraints. For example, you could define a
-btype "PosInt", a subtype of "Int" which only allows positive numbers.
+type "PosInt", a subtype of "Int" which only allows positive numbers.
=head2 Delegation
delegations. A delegation is a method which delegates the real work to
some attribute of the class.
-We saw this in the User example, where we define a delegation for the
-C<last_login_date()> method. Under the hood, this simple calls
+You saw this in the User example, where we defined a delegation for
+the C<last_login_date()> method. Under the hood, this simple calls
C<date()> on the User object's C<last_login_datetime> attribute.
=head2 Constructor
With Moose, this C<new()> method is created for you, and it simply
does the right thing. You should never need to define your own
-contsructor!
+constructor!
=head2 Destructor
=over 4
-=item * Moose class
+=item * Class
A package with no introspection other than mucking about in the symbol
table.
With Moose, you get well-defined declaration and introspection.
-=item * Moose attributes
+=item * Attributes
Hand-written accessor methods, symbol table hackery, or a helper
module like C<Class::Accessor>.
With Moose, these are declaritively defined, and distinct from
methods.
-=item * Moose method
+=item * Method
-These are pretty much the same in Moose.
+These are pretty much the same in Moose as in old school Perl.
=item * Roles
A C<new()> method which calls C<bless> on a reference.
-Comes for free when you define a class with moose.
+Comes for free when you define a class with Moose.
=item * Destructor
=head1 META WHAT?
A metaclass is a class that describes classes. With Moose, every class
-you define gets a C<meta()> method that you can call on the
-class. This returns a L<Moose::Meta::Class> object, which has an
-introspection API that can tell you about the class it represents.
+you define gets a C<meta()> method. It returns a L<Moose::Meta::Class>
+object, which has an introspection API that can tell you about the
+class it represents.
my $meta = User->meta();
One of the great things about Moose, is that if you dig down and find
that it does something the "wrong way", you can change it by extending
-its metaclasses. For example, you can have arrayref based objects, you
-can add your own types, you can make your constructors strict, you can
-define a naming scheme for attribute accessors, and much, much more.
+a metaclass. For example, you can have arrayref based objects, you can
+make your constructors strict (no unknown params allowed!), you can
+define a naming scheme for attribute accessors, you can make a class a
+Singleton, and much, much more.
Many of these extensions require surprisingly small amounts of code,
and once you've done it once, you'll never have to hand-code "your way
-of doing things" again.
+of doing things" again. Instead you ll just load your favorite
+extensions.
+
+ package MyWay::User;
+
+ use Moose;
+ use MooseX::StrictConstructor
+ use MooseX::MyWay;
+
+ has ...;
+
=head1 JUSTIFICATION
Yes.
-Moose has been used successfully in production environemnts by several
+Moose has been used successfully in production environments by several
people and companies. There are Moose applications which have been in
production with little or no issue now for well over two years. We
consider it highly stable and we are commited to keeping it stable.
=head1 AUTHOR
-Dave Rolsky E<lt>autarch@urth.orgE<gt> and Stevan Little Stevan Little
+Dave Rolsky E<lt>autarch@urth.orgE<gt> and Stevan Little
E<lt>stevan@iinteractive.comE<gt>
=head1 COPYRIGHT AND LICENSE
projects / gitmo/Moose.git / commitdiff