Type::Tiny::Manual::UsingWithMoo2 - phpMan

NAME
    Type::Tiny::Manual::UsingWithMoo2 - advanced use of Type::Tiny with Moo

MANUAL
  What is a Type?
    So far all the examples have shown you how to work with types, but we
    haven't looked at what a type actually *is*.

      use Types::Standard qw( Int );
      my $type = Int;

    "Int" in the above code is just a function called with zero arguments
    which returns a blessed Perl object. It is this object that defines what
    the Int type is and is responsible for checking values meet its
    definition.

      use Types::Standard qw( HashRef Int );
      my $type = HashRef[Int];

    The "HashRef" function, if called with no parameters returns the object
    defining the HashRef type, just like the "Int" function did before. But
    the difference here is that it's called with a parameter, an arrayref
    containing the Int type object. It uses this to make the HashRef[Int]
    type and returns that.

    Like any object, you can call methods on it. The most important methods
    to know about are:

      # check the value and return a boolean
      #
      $type->check($value);

      # return an error message about $value failing the type check
      # but don't actually check the value
      #
      $type->get_message($value);

      # coerce the value
      #
      my $coerced = $type->coerce($value);

    We've already seen some other methods earlier in the tutorial.

      # create a new type, same as the old type, but that has coercions
      #
      my $new_type = $type->plus_coercions( ... );

      # different syntax for parameterized types
      #
      my $href = HashRef;
      my $int = Int;
      my $href_of_int = $href->of($int);

    So now you should understand this:

      use Types::Standard qw( ArrayRef Dict Optional );
      use Types::Common::Numeric qw( PositiveInt );
      use Types::Common::String qw( NonEmptyStr );

      my $RaceInfo = Dict[
        year    => PositiveInt,
        race    => NonEmptyStr,
        jockey  => Optional[NonEmptyStr],
      ];

      has latest_event  => ( is => 'rw', isa => $RaceInfo );
      has wins          => ( is => 'rw', isa => ArrayRef[$RaceInfo] );
      has losses        => ( is => 'rw', isa => ArrayRef[$RaceInfo] );

    This can help you avoid repetition if you have a complex parameterized
    type that you need to reuse a few times.

  "where"
    One of the most useful methods you can call on a type object is "where".

      use Types::Standard qw( Int );

      has lucky_number => (
        is   => 'ro',
        isa  => Int->where(sub { $_ != 13 }),
      );

    I think you already understand what it does. It creates a new type
    constraint on the fly, restricting the original type.

    Like with coercions, these restrictions can be expressed as a coderef or
    as a string of Perl code, operating on the $_ variable. And like with
    coercions, using a string of code will result in better performance.

      use Types::Standard qw( Int );

      has lucky_number => (
        is   => 'ro',
        isa  => Int->where(q{ $_ != 13 }),
      );

    Let's coerce a hashref of strings from an even-sized arrayref of
    strings:

      use Types::Standard qw( HashRef ArrayRef Str );

      has stringhash => (
        is   => 'ro',
        isa  => HashRef->of(Str)->plus_coercions(
          ArrayRef->of(Str)->where(q{ @$_ % 2 == 0 }), q{
            my %h = @$_;
            \%h;
          },
        ),
        coerce => 1,  # never forget!
      );

    If you understand that, you really are in the advanced class.
    Congratulations!

  Unions
    Sometimes you want to accept one thing or another thing. This is pretty
    easy with Type::Tiny.

      use Types::Standard qw( HashRef ArrayRef Str );

      has strings => (
        is    => 'ro',
        isa   => ArrayRef[Str] | HashRef[Str],
      );

    Type::Tiny overloads the bitwise or operator so stuff like this should
    "just work".

    That said, now any code that calls "$self->strings" will probably need
    to check if the value is an arrayref or a hashref before doing anything
    with it. So it may be simpler overall if you just choose one of the
    options and coerce the other one into it.

  Intersections
    Similar to a union is an intersection.

      package MyAPI::Client {
        use Moo;
        use Types::Standard qw( HasMethods InstanceOf );

        has ua => (
          is    => 'ro',
          isa   => (InstanceOf["MyUA"]) & (HasMethods["store_cookie"]),
        );
      }

    Here we are checking that the UA is an instance of the MyUA class and
    also offers the "store_cookie" method. Perhaps "store_cookie" isn't
    provided by the MyUA class itself, but several subclasses of MyUA
    provide it.

    Intersections are not useful as often as unions are. This is because
    they often make no sense. "(ArrayRef) & (HashRef)" would be a reference
    which was simultaneously pointing to an array and a hash, which is
    impossible.

    Note that when using intersections, it is good practice to put
    parentheses around each type. This is to disambiguate the meaning of "&"
    for Perl, because Perl uses it as the bitwise and operator but also as
    the sigil for subs.

  Complements
    For any type Foo there is a complementary type ~Foo (pronounced "not
    Foo").

      package My::Class {
        use Moo;
        use Types::Standard qw( ArrayRef CodeRef );

        has things => ( is => 'ro', isa => ArrayRef[~CodeRef] );
      }

    "things" is now an arrayref of anything except coderefs.

    If you need a number that is *not* an integer:

      Num & ~Int

    Types::Standard includes two types which are complements of each other:
    Undef and Defined.

    NegativeInt might seem to be the complement of PositiveOrZeroInt but
    when you think about it, it is not. There are values that fall into
    neither category, such as non-integers, non-numeric strings, references,
    undef, etc.

  "stringifies_to" and "numifies_to"
    The Object type constraint provides "stringifies_to" and "numifies_to"
    methods which are probably best explained by examples.

    "Object->numifies_to(Int)" means any object where "0 + $object" is an
    integer.

    "Object->stringifies_to(StrMatch[$re])" means any object where "$object"
    matches the regular expression.

    "Object->stringifies_to($re)" also works as a shortcut.

    "Object->numifies_to($coderef)" and "Object->stringifies_to($coderef)"
    also work, where the coderef checks $_ and returns a boolean.

    Other types which are also logically objects, such as parameterized
    HasMethods, InstanceOf, and ConsumerOf should also provide
    "stringifies_to" and "numifies_to" methods.

    "stringifies_to" and "numifies_to" work on unions if *all* of the type
    constraints in the union offer the method.

    "stringifies_to" and "numifies_to" work on intersections if *at least
    one of* of the type constraints in the intersection offers the method.

  "with_attribute_values"
    Another one that is probably best explained using an example:

      package Horse {
        use Types::Standard qw( Enum Object );

        has gender  => (
          is  => 'ro',
          isa => Enum['m', 'f'],
        );
        has father  => (
          is  => 'ro',
          isa => Object->with_attribute_values(gender => Enum['m']),
        );
        has mother  => (
          is  => 'ro',
          isa => Object->with_attribute_values(gender => Enum['f']),
        );
      }

    In this example when you set a horse's father, it will call
    "$father->gender" and check that it matches Enum['m'].

    This method is in the same family as "stringifies_as" and "numifies_as",
    so like those, it only applies to Object and similar type constraints,
    can work on unions/intersections under the same circumstances, and will
    also accept coderefs and regexps.

      has father  => (
        is  => 'ro',
        isa => Object->with_attribute_values(gender => sub { $_ eq 'm' }),
      );
      has mother  => (
        is  => 'ro',
        isa => Object->with_attribute_values(gender => qr/^f/i),
      );

    All of "stringifies_as", "numifies_as", and "with_attributes_as" are
    really just wrappers around "where". The following two are roughly
    equivalent:

      my $type1 = Object->with_attribute_values(foo => Int, bar => Num);

      my $type2 = Object->where(sub {
        Int->check( $_->foo ) and Num->check( $_->bar )
      });

    The first will result in better performing code though.

  Tied Variables
    It is possible to tie variables to a type constraint.

      use Types::Standard qw(Int);

      tie my $n, Int, 4;

      print "$n\n";   # says "4"
      $n = 5;         # ok
      $n = "foo";     # dies

    This feature requires Type::Tie which is a separate thing to install.
    Type::Tiny will automatically load Type::Tie in the background if it
    detects you're trying to tie a variable to a type.

    You can also tie arrays:

      tie my @numbers, Int;
      push @numbers, 1 .. 10;

    And hashes:

      tie my %numbers, Int;
      $numbers{lucky}   = 7;
      $numbers{unlucky} = 13;

    Earlier in the manual, it was mentioned that there is a problem with
    code like this:

      push @{ $horse->children }, $non_horse;

    This can be solved using tied variables.

      tie @{ $horse->children }, InstanceOf["Horse"];

    Here is a longer example using builders and triggers.

      package Horse {
        use Moo;
        use Types::Standard qw( Str Num ArrayRef InstanceOf );
        use Type::Params qw(compile);
        use namespace::autoclean;

        my $ThisClass = InstanceOf[ __PACKAGE__ ];

        has name       => ( is => 'ro',    isa => Str );
        has gender     => ( is => 'ro',    isa => Str );
        has age        => ( is => 'rw',    isa => Num );
        has children   => (
          is        => 'rw',
          isa       => ArrayRef[$ThisClass],
          builder   => "_build_children",
          trigger   => sub { shift->_trigger_children(@_) },
        );

        # tie a default arrayref
        sub _build_children {
          my $self = shift;
          tie my @kids, $ThisClass;
          \@kids;
        }

        # this method will tie an arrayref provided by the caller
        sub _trigger_children {
          my $self = shift;
          my ($new) = @_;
          tie @$new, $ThisClass;
        }

        sub add_child {
          state $check = compile($ThisClass, $ThisClass);
          my ($self, $kid) = &$check;
          push @{ $self->children }, $kid;
          return $self;
        }
      }

    Now it's pretty much impossible for the caller to make a mess by adding
    a non-horse as a child.

NEXT STEPS
    Here's your next step:

    *   Type::Tiny::Manual::UsingWithMoo3

        There's more than one way to do it! Alternative ways of using
        Type::Tiny, including type registries, exported functions, and
        "dwim_type".

AUTHOR
    Toby Inkster <tobyink AT cpan.org>.

COPYRIGHT AND LICENCE
    This software is copyright (c) 2013-2014, 2017-2021 by Toby Inkster.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.

DISCLAIMER OF WARRANTIES
    THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
    WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
    MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.