Object::Pad::MOP::FielUserrContributed Perl DoObject::Pad::MOP::FieldAttr(3pm)
NAME
"Object::Pad::MOP::FieldAttr" - meta-object representation of a field
attribute for "Object::Pad"
DESCRIPTION
This API provides a way for pure-perl implementations of field
attributes to be provided. Pure-perl attributes cannot currently add
new behaviour to the way that fields work, but they do provide a means
for class authors to annotate extra metadata onto fields, that can be
queried by other code.
Primilarily this is done by using the "get_attribute_value" in
Object::Pad::MOP::Field accessor method on a field metadata instance.
This API should be considered experimental, and will emit warnings to
that effect. They can be silenced with
use Object::Pad qw( :experimental(custom_field_attr) );
METHODS
register
Object::Pad::MOP::FieldAttr->register( $name, %args )
Since version 0.60.
Creates a new field attribute of the given name. The name must begin
with a capital letter, in order to distinguish this from any of the
built-in core attributes, whose names are lowercase.
The attribute is only available if the hints hash contains a key of the
name given by the attribute's "permit_hintkey" argument. This would
typically be set in the hints hash by the "import" method of the module
implementing it, and would be named based on the name of the module
providing the attribute:
sub import { $^H{"Some::Package::Name/Attrname"} }
Takes the following additional named arguments:
permit_hintkey => STRING
Required. A string giving a key that must be found in the hints
hash ("%^H") for this attribute name to be visible.
apply => CODE
An optional code reference for a callback function to invoke when
the attribute is applied to a field. If present, it is passed the
field metadata instance as a Object::Pad::MOP::Field reference, and
a string containing the contents of the attribute's parenthesized
value. The return value of the callback will be stored as the
attribute's value and can be accessed by the "get_attribute_value"
method on the field metadata.
$result = $apply->( $fieldmeta, $value )
If the "apply" callback is absent then the string value itself is
stored.
AUTHOR
Paul Evans <leonerd@leonerd.org.uk>
perl v5.36.0 2023-01-13 Object::Pad::MOP::FieldAttr(3pm)
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