NAME

Sub::HandlesVia::Handler - template for a method that can be delegated to

DESCRIPTION

This module is part of Sub::HandlesVia's internal API. It is mostly of interest to people extending Sub::HandlesVia.

This module works in conjunction with Sub::HandlesVia::CodeGenerator and subclasses of Sub::HandlesVia::Toolkit to build a string of Perl code which can be compiled into a method to install into your class.

CONSTRUCTORS

new( %attributes )

Standard Moose-like constructor.

lookup( $method, $trait )

Looks up a method from existing handler libraries.

  my $h = Sub::HandlesVia::Handler->lookup( 'get', 'Array' );

Curried version:

  my $h = Sub::HandlesVia::Handler->lookup( [ 'get', 0 ], 'Array' );

The $trait may be an arrayref of possible traits.

EXPORTS

Nothing is exported by default.

handler %attributes

Shortcut for the new constructor.

  use Sub::HandlesVia::Handler 'handler';
  
  my $h = handler( %attr );
  # is the same as
  my $h = Sub::HandlesVia::Handler->new( %attr );

ATTRIBUTES

name Str

The name of the function being delegated to.

is_mutator Bool

Indicates whether this handler might mutate an attribute value. The default is to try to detect it based on analysis of the templates.

template Str

Specially formatted string (see section below) containing the Perl code to implement the method.

lvalue_template Maybe[Str]

If defined, a shortcut for implementing it when the attribute slot value can be used as an lvalue.

args Maybe[PositiveOrZeroInt]

The number of arguments which the method being generated expects (does not include the attibute value itself).

min_args and max_args Maybe[PositiveOrZeroInt]

For methods which take a variable number of arguments. If omitted, default to args.

signature Maybe[ArrayRef[TypeTiny]]

A signature for said arguments.

usage Str

A signature to show in documentation, like '$index, $value'. If not provided, will be generated magically from args, min_args, and max_args.

curried Maybe[ArrayRef[Item]]

An arrayref of curried arguments.

is_chainable Bool

Whether to force the generated method to be chainable.

no_validation_needed Bool

Whether to do less validation of input data.

default_for_reset Maybe[Str]

If this handler has to "reset" an attribute value to its default, and the attribute doesn't have a default, this string of Perl code is evaluated to provide a default. An example might be "[]".

prefer_shift_self Bool

Indicates this handler would prefer the code generator to shift $self off @_.

documentation Maybe[Str]

String of pod to describe the handler.

_examples Maybe[CodeRef]

This coderef, if called with parameters $class, $attr, and $method, will generate a code example to insert into the pod.

additional_validation Maybe[CodeRef]

Coderef providing a slightly annoying API. To be described later.

allow_getter_shortcuts Bool

Defaults to true. Rarely useful to override.

METHODS

has_min_args() and has_max_args()

Indicate whether this handler has a defined min or max args.

install_method( %args )

The required arguments are method_name and code_generator. Installs the delegated method into the target class (taken from the code generator).

code_as_string( %args )

Same required arguments as install_method, but returns the Perl code for the method as a string.

curry( @args )

Pseudo-constructor.

Creates a new Sub::HandlesVia::Handler object like this one, but with the given arguments curried.

loose

Pseudo-constructor.

Creates a new Sub::HandlesVia::Handler object like this one, but with looser argument validation.

chainable

Pseudo-constructor.

Creates a new Sub::HandlesVia::Handler object like this one, but chainable.

TEMPLATE FORMAT

The template is a string of Perl code, except if the following special things are found in it, they are substituted.

$SELF

The invocant.

$SLOT

Direct hashref access for the attribute.

$GET

The current value of the attribute.

@ARG

Any additional arguments passed to the delegated method.

$ARG[$n] will also work.

#ARG

The number of additional arguments passed to the delegated method.

$ARG

The first element in @ARG.

$DEFAULT

The attribute's default value, if known.

« EXPR »

An expression in double angled quotes sets the attribute's value to the expression.

For example, a handler to halve the value of a numeric attribute might be:

  'Sub::HandlesVia::Handler'->new(
    name => 'MyNumber:halve',
    args => 0,
    template => '« $GET / 2 »',
    lvalue_template => '$GET /= 2',
  );

SUBCLASSES

Sub::HandlesVia::Handler::Traditional and Sub::HandlesVia::Handler::CodeRef are provided. See source code for this module for more info.

BUGS

Please report any bugs to https://github.com/tobyink/p5-sub-handlesvia/issues.

SEE ALSO

Sub::HandlesVia.

AUTHOR

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

This software is copyright (c) 2020, 2022 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.