Provided by: libmoosex-types-structured-perl_0.35-1_all 
NAME
MooseX::Types::Structured - Structured Type Constraints for Moose
VERSION
version 0.35
SYNOPSIS
The following is example usage for this module.
package Person;
use Moose;
use MooseX::Types::Moose qw(Str Int HashRef);
use MooseX::Types::Structured qw(Dict Tuple Optional);
## A name has a first and last part, but middle names are not required
has name => (
isa=>Dict[
first => Str,
last => Str,
middle => Optional[Str],
],
);
## description is a string field followed by a HashRef of tagged data.
has description => (
isa=>Tuple[
Str,
Optional[HashRef],
],
);
## Remainder of your class attributes and methods
Then you can instantiate this class with something like:
my $john = Person->new(
name => {
first => 'John',
middle => 'James'
last => 'Napiorkowski',
},
description => [
'A cool guy who loves Perl and Moose.', {
married_to => 'Vanessa Li',
born_in => 'USA',
};
]
);
Or with:
my $vanessa = Person->new(
name => {
first => 'Vanessa',
last => 'Li'
},
description => ['A great student!'],
);
But all of these would cause a constraint error for the "name" attribute:
## Value for 'name' not a HashRef
Person->new( name => 'John' );
## Value for 'name' has incorrect hash key and missing required keys
Person->new( name => {
first_name => 'John'
});
## Also incorrect keys
Person->new( name => {
first_name => 'John',
age => 39,
});
## key 'middle' incorrect type, should be a Str not a ArrayRef
Person->new( name => {
first => 'Vanessa',
middle => [1,2],
last => 'Li',
});
And these would cause a constraint error for the "description" attribute:
## Should be an ArrayRef
Person->new( description => 'Hello I am a String' );
## First element must be a string not a HashRef.
Person->new (description => [{
tag1 => 'value1',
tag2 => 'value2'
}]);
Please see the test cases for more examples.
DESCRIPTION
A structured type constraint is a standard container Moose type constraint, such as an
"ArrayRef" or "HashRef", which has been enhanced to allow you to explicitly name all the
allowed type constraints inside the structure. The generalized form is:
TypeConstraint[@TypeParameters or %TypeParameters]
Where "TypeParameters" is an array reference or hash references of
Moose::Meta::TypeConstraint objects.
This type library enables structured type constraints. It is built on top of the
MooseX::Types library system, so you should review the documentation for that if you are
not familiar with it.
Comparing Parameterized types to Structured types
Parameterized constraints are built into core Moose and you are probably already familiar
with the type constraints "HashRef" and "ArrayRef". Structured types have similar
functionality, so their syntax is likewise similar. For example, you could define a
parameterized constraint like:
subtype ArrayOfInts,
as ArrayRef[Int];
which would constrain a value to something like [1,2,3,...] and so on. On the other hand,
a structured type constraint explicitly names all it's allowed 'internal' type parameter
constraints. For the example:
subtype StringFollowedByInt,
as Tuple[Str,Int];
would constrain its value to things like "['hello', 111]" but "['hello', 'world']" would
fail, as well as "['hello', 111, 'world']" and so on. Here's another example:
package MyApp::Types;
use MooseX::Types -declare [qw(StringIntOptionalHashRef)];
use MooseX::Types::Moose qw(Str Int);
use MooseX::Types::Structured qw(Tuple Optional);
subtype StringIntOptionalHashRef,
as Tuple[
Str, Int,
Optional[HashRef]
];
This defines a type constraint that validates values like:
['Hello', 100, {key1 => 'value1', key2 => 'value2'}];
['World', 200];
Notice that the last type constraint in the structure is optional. This is enabled via
the helper "Optional" type constraint, which is a variation of the core Moose type
constraint "Maybe". The main difference is that "Optional" type constraints are required
to validate if they exist, while "Maybe" permits undefined values. So the following
example would not validate:
StringIntOptionalHashRef->validate(['Hello Undefined', 1000, undef]);
Please note the subtle difference between undefined and null. If you wish to allow both
null and undefined, you should use the core Moose "Maybe" type constraint instead:
package MyApp::Types;
use MooseX::Types -declare [qw(StringIntMaybeHashRef)];
use MooseX::Types::Moose qw(Str Int Maybe);
use MooseX::Types::Structured qw(Tuple);
subtype StringIntMaybeHashRef,
as Tuple[
Str, Int, Maybe[HashRef]
];
This would validate the following:
['Hello', 100, {key1 => 'value1', key2 => 'value2'}];
['World', 200, undef];
['World', 200];
Structured constraints are not limited to arrays. You can define a structure against a
"HashRef" with the "Dict" type constraint as in this example:
subtype FirstNameLastName,
as Dict[
firstname => Str,
lastname => Str,
];
This would constrain a "HashRef" that validates something like:
{firstname => 'Christopher', lastname => 'Parsons'};
but all the following would fail validation:
## Incorrect keys
{first => 'Christopher', last => 'Parsons'};
## Too many keys
{firstname => 'Christopher', lastname => 'Parsons', middlename => 'Allen'};
## Not a HashRef
['Christopher', 'Parsons'];
These structures can be as simple or elaborate as you wish. You can even combine various
structured, parameterized and simple constraints all together:
subtype Crazy,
as Tuple[
Int,
Dict[name=>Str, age=>Int],
ArrayRef[Int]
];
Which would match:
[1, {name=>'John', age=>25},[10,11,12]];
Please notice how the type parameters can be visually arranged to your liking and to
improve the clarity of your meaning. You don't need to run then altogether onto a single
line. Additionally, since the "Dict" type constraint defines a hash constraint, the key
order is not meaningful. For example:
subtype AnyKeyOrder,
as Dict[
key1=>Int,
key2=>Str,
key3=>Int,
];
Would validate both:
{key1 => 1, key2 => "Hi!", key3 => 2};
{key2 => "Hi!", key1 => 100, key3 => 300};
As you would expect, since underneath it's just a plain old Perl hash at work.
Alternatives
You should exercise some care as to whether or not your complex structured constraints
would be better off contained by a real object as in the following example:
package MyApp::MyStruct;
use Moose;
## lazy way to make a bunch of attributes
has $_ for qw(full_name age_in_years);
package MyApp::MyClass;
use Moose;
has person => (isa => 'MyApp::MyStruct');
my $instance = MyApp::MyClass->new(
person=>MyApp::MyStruct->new(
full_name => 'John',
age_in_years => 39,
),
);
This method may take some additional time to set up but will give you more flexibility.
However, structured constraints are highly compatible with this method, granting some
interesting possibilities for coercion. Try:
package MyApp::MyClass;
use Moose;
use MyApp::MyStruct;
## It's recommended your type declarations live in a separate class in order
## to promote reusability and clarity. Inlined here for brevity.
use MooseX::Types::DateTime qw(DateTime);
use MooseX::Types -declare [qw(MyStruct)];
use MooseX::Types::Moose qw(Str Int);
use MooseX::Types::Structured qw(Dict);
## Use class_type to create an ISA type constraint if your object doesn't
## inherit from Moose::Object.
class_type 'MyApp::MyStruct';
## Just a shorter version really.
subtype MyStruct,
as 'MyApp::MyStruct';
## Add the coercions.
coerce MyStruct,
from Dict[
full_name=>Str,
age_in_years=>Int
], via {
MyApp::MyStruct->new(%$_);
},
from Dict[
lastname=>Str,
firstname=>Str,
dob=>DateTime
], via {
my $name = $_->{firstname} .' '. $_->{lastname};
my $age = DateTime->now - $_->{dob};
MyApp::MyStruct->new(
full_name=>$name,
age_in_years=>$age->years,
);
};
has person => (isa=>MyStruct);
This would allow you to instantiate with something like:
my $obj = MyApp::MyClass->new( person => {
full_name=>'John Napiorkowski',
age_in_years=>39,
});
Or even:
my $obj = MyApp::MyClass->new( person => {
lastname=>'John',
firstname=>'Napiorkowski',
dob=>DateTime->new(year=>1969),
});
If you are not familiar with how coercions work, check out the Moose cookbook entry
Moose::Cookbook::Recipe5 for an explanation. The section "Coercions" has additional
examples and discussion.
Subtyping a Structured type constraint
You need to exercise some care when you try to subtype a structured type as in this
example:
subtype Person,
as Dict[name => Str];
subtype FriendlyPerson,
as Person[
name => Str,
total_friends => Int,
];
This will actually work BUT you have to take care that the subtype has a structure that
does not contradict the structure of it's parent. For now the above works, but I will
clarify the syntax for this at a future point, so it's recommended to avoid (should not
really be needed so much anyway). For now this is supported in an EXPERIMENTAL way. Your
thoughts, test cases and patches are welcomed for discussion. If you find a good use for
this, please let me know.
Coercions
Coercions currently work for 'one level' deep. That is you can do:
subtype Person,
as Dict[
name => Str,
age => Int
];
subtype Fullname,
as Dict[
first => Str,
last => Str
];
coerce Person,
## Coerce an object of a particular class
from BlessedPersonObject, via {
+{
name=>$_->name,
age=>$_->age,
};
},
## Coerce from [$name, $age]
from ArrayRef, via {
+{
name=>$_->[0],
age=>$_->[1],
},
},
## Coerce from {fullname=>{first=>...,last=>...}, dob=>$DateTimeObject}
from Dict[fullname=>Fullname, dob=>DateTime], via {
my $age = $_->dob - DateTime->now;
my $firstn = $_->{fullname}->{first};
my $lastn = $_->{fullname}->{last}
+{
name => $_->{fullname}->{first} .' '. ,
age =>$age->years
}
};
And that should just work as expected. However, if there are any 'inner' coercions, such
as a coercion on "Fullname" or on "DateTime", that coercion won't currently get activated.
Please see the test 07-coerce.t for a more detailed example. Discussion on extending
coercions to support this welcome on the Moose development channel or mailing list.
Recursion
Newer versions of MooseX::Types support recursive type constraints. That is you can
include a type constraint as a contained type constraint of itself. For example:
subtype Person,
as Dict[
name=>Str,
friends=>Optional[
ArrayRef[Person]
],
];
This would declare a "Person" subtype that contains a name and an optional "ArrayRef" of
"Person"s who are friends as in:
{
name => 'Mike',
friends => [
{ name => 'John' },
{ name => 'Vincent' },
{
name => 'Tracey',
friends => [
{ name => 'Stephenie' },
{ name => 'Ilya' },
],
},
],
};
Please take care to make sure the recursion node is either "Optional", or declare a union
with an non-recursive option such as:
subtype Value
as Tuple[
Str,
Str|Tuple,
];
Which validates:
[
'Hello', [
'World', [
'Is', [
'Getting',
'Old',
],
],
],
];
Otherwise you will define a subtype that is impossible to validate since it is infinitely
recursive. For more information about defining recursive types, please see the
documentation in MooseX::Types and the test cases.
TYPE CONSTRAINTS
This type library defines the following constraints.
Tuple[@constraints]
This defines an ArrayRef based constraint which allows you to validate a specific list of
contained constraints. For example:
Tuple[Int,Str]; ## Validates [1,'hello']
Tuple[Str|Object, Int]; ## Validates ['hello', 1] or [$object, 2]
The Values of @constraints should ideally be MooseX::Types declared type constraints. We
do support 'old style' Moose string based constraints to a limited degree but these string
type constraints are considered deprecated. There will be limited support for bugs
resulting from mixing string and MooseX::Types in your structures. If you encounter such
a bug and really need it fixed, we will required a detailed test case at the minimum.
Dict[%constraints]
This defines a HashRef based constraint which allowed you to validate a specific hashref.
For example:
Dict[name=>Str, age=>Int]; ## Validates {name=>'John', age=>39}
The keys in %constraints follow the same rules as @constraints in the above section.
Map[ $key_constraint, $value_constraint ]
This defines a "HashRef"-based constraint in which both the keys and values are required
to meet certain constraints. For example, to map hostnames to IP addresses, you might
say:
Map[ HostName, IPAddress ]
The type constraint would only be met if every key was a valid "HostName" and every value
was a valid "IPAddress".
Optional[$constraint]
This is primarily a helper constraint for "Dict" and "Tuple" type constraints. What this
allows is for you to assert that a given type constraint is allowed to be null (but NOT
undefined). If the value is null, then the type constraint passes but if the value is
defined it must validate against the type constraint. This makes it easy to make a Dict
where one or more of the keys doesn't have to exist or a tuple where some of the values
are not required. For example:
subtype Name() => as Dict[
first=>Str,
last=>Str,
middle=>Optional[Str],
];
...creates a constraint that validates against a hashref with the keys 'first' and 'last'
being strings and required while an optional key 'middle' is must be a string if it
appears but doesn't have to appear. So in this case both the following are valid:
{first=>'John', middle=>'James', last=>'Napiorkowski'}
{first=>'Vanessa', last=>'Li'}
If you use the "Maybe" type constraint instead, your values will also validate against
"undef", which may be incorrect for you.
EXPORTABLE SUBROUTINES
This type library makes available for export the following subroutines
slurpy
Structured type constraints by their nature are closed; that is validation will depend on
an exact match between your structure definition and the arguments to be checked.
Sometimes you might wish for a slightly looser amount of validation. For example, you may
wish to validate the first 3 elements of an array reference and allow for an arbitrary
number of additional elements. At first thought you might think you could do it this way:
# I want to validate stuff like: [1,"hello", $obj, 2,3,4,5,6,...]
subtype AllowTailingArgs,
as Tuple[
Int,
Str,
Object,
ArrayRef[Int],
];
However what this will actually validate are structures like this:
[10,"Hello", $obj, [11,12,13,...] ]; # Notice element 4 is an ArrayRef
In order to allow structured validation of, "and then some", arguments, you can use the
"slurpy" method against a type constraint. For example:
use MooseX::Types::Structured qw(Tuple slurpy);
subtype AllowTailingArgs,
as Tuple[
Int,
Str,
Object,
slurpy ArrayRef[Int],
];
This will now work as expected, validating ArrayRef structures such as:
[1,"hello", $obj, 2,3,4,5,6,...]
A few caveats apply. First, the slurpy type constraint must be the last one in the list
of type constraint parameters. Second, the parent type of the slurpy type constraint must
match that of the containing type constraint. That means that a "Tuple" can allow a
slurpy "ArrayRef" (or children of "ArrayRef"s, including another "Tuple") and a "Dict" can
allow a slurpy "HashRef" (or children/subtypes of HashRef, also including other "Dict"
constraints).
Please note the technical way this works 'under the hood' is that the slurpy keyword
transforms the target type constraint into a coderef. Please do not try to create your
own custom coderefs; always use the slurpy method. The underlying technology may change
in the future but the slurpy keyword will be supported.
ERROR MESSAGES
Error reporting has been improved to return more useful debugging messages. Now I will
stringify the incoming check value with Devel::PartialDump so that you can see the actual
structure that is tripping up validation. Also, I report the 'internal' validation error,
so that if a particular element inside the Structured Type is failing validation, you will
see that. There's a limit to how deep this internal reporting goes, but you shouldn't see
any of the "failed with ARRAY(XXXXXX)" that we got with earlier versions of this module.
This support is continuing to expand, so it's best to use these messages for debugging
purposes and not for creating messages that 'escape into the wild' such as error messages
sent to the user.
Please see the test '12-error.t' for a more lengthy example. Your thoughts and preferable
tests or code patches very welcome!
EXAMPLES
Here are some additional example usage for structured types. All examples can be found
also in the 't/examples.t' test. Your contributions are also welcomed.
Normalize a HashRef
You need a hashref to conform to a canonical structure but are required accept a bunch of
different incoming structures. You can normalize using the "Dict" type constraint and
coercions. This example also shows structured types mixed which other MooseX::Types
libraries.
package Test::MooseX::Meta::TypeConstraint::Structured::Examples::Normalize;
use Moose;
use DateTime;
use MooseX::Types::Structured qw(Dict Tuple);
use MooseX::Types::DateTime qw(DateTime);
use MooseX::Types::Moose qw(Int Str Object);
use MooseX::Types -declare => [qw(Name Age Person)];
subtype Person,
as Dict[
name=>Str,
age=>Int,
];
coerce Person,
from Dict[
first=>Str,
last=>Str,
years=>Int,
], via { +{
name => "$_->{first} $_->{last}",
age => $_->{years},
}},
from Dict[
fullname=>Dict[
last=>Str,
first=>Str,
],
dob=>DateTime,
],
## DateTime needs to be inside of single quotes here to disambiguate the
## class package from the DataTime type constraint imported via the
## line "use MooseX::Types::DateTime qw(DateTime);"
via { +{
name => "$_->{fullname}{first} $_->{fullname}{last}",
age => ($_->{dob} - 'DateTime'->now)->years,
}};
has person => (is=>'rw', isa=>Person, coerce=>1);
And now you can instantiate with all the following:
__PACKAGE__->new(
person=>{
name=>'John Napiorkowski',
age=>39,
},
);
__PACKAGE__->new(
person=>{
first=>'John',
last=>'Napiorkowski',
years=>39,
},
);
__PACKAGE__->new(
person=>{
fullname => {
first=>'John',
last=>'Napiorkowski'
},
dob => 'DateTime'->new(
year=>1969,
month=>2,
day=>13
),
},
);
This technique is a way to support various ways to instantiate your class in a clean and
declarative way.
SEE ALSO
The following modules or resources may be of interest.
Moose, MooseX::Types, Moose::Meta::TypeConstraint,
MooseX::Meta::TypeConstraint::Structured
SUPPORT
Bugs may be submitted through the RT bug tracker
<https://rt.cpan.org/Public/Dist/Display.html?Name=MooseX-Types-Structured> (or
bug-MooseX-Types-Structured@rt.cpan.org <mailto:bug-MooseX-Types-Structured@rt.cpan.org>).
There is also a mailing list available for users of this distribution, at
<http://lists.perl.org/list/moose.html>.
There is also an irc channel available for users of this distribution, at
<irc://irc.perl.org/#moose>.
AUTHORS
• John Napiorkowski <jjnapiork@cpan.org>
• Florian Ragwitz <rafl@debian.org>
• XXXX XXX'XX (Yuval Kogman) <nothingmuch@woobling.org>
• Tomas (t0m) Doran <bobtfish@bobtfish.net>
• Robert Sedlacek <rs@474.at>
CONTRIBUTORS
• Karen Etheridge <ether@cpan.org>
• Ricardo Signes <rjbs@cpan.org>
• Dave Rolsky <autarch@urth.org>
• Ansgar Burchardt <ansgar@43-1.org>
• Stevan Little <stevan.little@iinteractive.com>
• arcanez <justin.d.hunter@gmail.com>
• Jesse Luehrs <doy@tozt.net>
• D. Ilmari Mannsaaker <ilmari@cpan.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2008 by John Napiorkowski.
This is free software; you can redistribute it and/or modify it under the same terms as
the Perl 5 programming language system itself.