NAME

Actionable - auto-populate Raku classes from grammar match objects

SYNOPSIS

use Actionable;

class Item does Actionable {
    has Str  $.description;
    has Real $.hours;
    has Real $.rate;
    method subtotal { $.hours * $.rate }
}

class Invoice does Actionable {
    has Str  $.id       is rw = "";
    has Str  $.date     is rw = "";
    has Str  $.client   is rw = "";
    has Real $.tax-rate is rw = 0.0;
    has Item @.items;
    method transform(Str $attr, $raw) {
        $attr eq 'tax-rate' ?? $raw / 100 !! $raw
    }
}

class Actions {
    method TOP($/) {
        my $inv = Invoice.action($<invoice-line>);  # create from type object
        $inv.action($_) for $<field-line>;           # update existing instance
        $inv.items.push(Item.action($_)) for $<item-line>;
        make $inv;
    }
}

DESCRIPTION

Actionable is a role that eliminates boilerplate in Raku grammar Actions classes. Mix it into any class to get an action method that auto-populates attributes from a grammar match object.

action dispatches on whether the invocant is defined:

• Type object (MyClass.action($match)) — creates and returns a new instance, populating scalar attributes from named captures in $match.

• Instance ($obj.action($match)) — updates the instance in place from $match and returns self.

Attribute mapping

By default each attribute is looked up by its own name as a named capture. To override, provide a capture-map method returning a Hash of attr-name =E<gt> dot-path:

method capture-map {
    { qty   => 'number.0',   # $match<number>[0]
      price => 'number.1' }  # $match<number>[1]
}

Dot-path segments are hash keys or array indices (all-digit segments are treated as indices).

Alternatively, use Raku's aliased capture syntax in the grammar to name captures after the target attribute — avoiding capture-map entirely:

rule item-line { item <description=quoted-string> hours <hours=number> rate <rate=number> }

Type coercion

Attributes typed as Numeric (or any subtype: Int, Real, Rat, Num) are coerced with +; all others with ~. Array and hash attributes are skipped automatically.

Post-coercion transforms

Override transform to adjust a value after coercion:

method transform(Str $attr, $raw) {
    $attr eq 'tax-rate' ?? $raw / 100 !! $raw
}

AUTHOR

librasteve librasteve@furnival.net

COPYRIGHT AND LICENSE

Copyright 2026 librasteve

This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.