NAME

       "Object::Pad::MOP::SlotAttr" - meta-object representation of a slot attribute for
       "Object::Pad"

DESCRIPTION

       This API provides a way for pure-perl implementations of slot attributes to be provided.
       Pure-perl attributes cannot currently add new behaviour to the way that slots work, but
       they do provide a means for class authors to annotate extra metadata onto slots, that can
       be queried by other code.

       Primilarily this is done by using the "get_attribute_value" in Object::Pad::MOP::Slot
       accessor method on a slot metadata instance.

METHODS

   register
          Object::Pad::MOP::SlotAttr->register( $name, %args )

       Since version 0.57.

       Creates a new slot 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 slot. If present, it is passed the slot metadata instance as a
           Object::Pad::MOP::Slot 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
           slot metadata.

              $result = $apply->( $slotmeta, $value )

           If the "apply" callback is absent then the string value itself is stored.

AUTHOR

       Paul Evans <leonerd@leonerd.org.uk>