class Metamodel::Primitives
Metaobject that supports low-level type operations
Metamodel::Primitives
provides low-level operations for working with types, which are otherwise only available as implementation-dependent directives. These primitives are available as class methods.
Here is an example that steals the metamodel instance from the Int class to create a custom type (usually you would create your own metaclass if you mess with something as low-level), which allows calling of just one method called why
:
my Mu := Metamodel::Primitives.create_type(Int.HOW, 'P6opaque');.^set_name('why oh why?');my = why => sub ($) ;Metamodel::Primitives.install_method_cache(, , :authoritative);.why; # 42.list;CATCH ;# OUTPUT: «X::Method::NotFound: Method 'list' not found for invocant of class 'why oh why?'»
Methods
method create_type
method create_type(Mu , = 'P6opaque')
Creates and returns a new type from a metaobject $how
and a representation name.
method set_package
method set_package(Mu , )
Sets the package associated with the type.
method install_method_cache
method install_method_cache( Mu , , : = True)
Installs a method cache, that is, a mapping from method names to code objects. If :authoritative
is missing, or set to True
, then calls of methods that do not exist in the cache will throw an exception of type X::Method::NotFound. If :authoritative
is set to False
, the usual fallback mechanism are tried.
method configure_type_checking
method configure_type_checking( Mu , , : = True, : = False )
Configures the type checking for $type
. @cache
is a list of known types against which $type
checks positively (so in a classical class-based system, the type itself and all recursive superclasses). If :authoritative
is missing or True
, this type will fail checks against all types not in @cache
. If :call_accepts
is True, the method ACCEPTS will be called for type checks against this type.
method configure_destroy
method configure_destroy(Mu , )
Configures whether DESTROY
methods are called (if present) when the garbage collector collects an object of this type (if $destroy
is set to a true value). This comes with a performance overhead, so should only be set to a true value if necessary.
method compose_type
method compose_type(Mu , )
Composes $type
(that is, finalizes it to be ready for instantiation). See https://github.com/perl6/nqp/blob/master/docs/6model/repr-compose-protocol.markdown for what $configuration
can contain (until we have better docs, sorry).
method rebless
method rebless(Mu , Mu )
Changes $obj
to be of type $type
. This only works if $type
type-checks against the current type of $obj
, and if the storage of $object
is a subset of that of $type
.
method is_type
method is_type(Mu \obj, Mu \type --> Bool)
Type-checks obj
against type