The metaobject protocol .^

Introspect types through their metaobject — MRO, parents, attributes, and signatures.

The .^ operator calls a metamethod — a method on a type's metaobject — to ask about its structure: its ancestors, attributes, and more.

Method resolution order — .^mro #

.^mro lists a type and its ancestors, in the order methods are resolved.

say Int.^mro.map(*.^name);

(Int Cool Any Mu)

Attributes — .^attributes #

.^attributes returns a class's attributes; .name gives each one's $!-twigil name.

class Point { has $.x; has $.y }
say Point.^attributes.map(*.name);

($!x $!y)

Introspecting a routine's signature #

&sub.signature.params returns the parameter objects, so you can inspect a routine's interface reflectively.

sub area($w, $h) {}
say &area.signature.params.map(*.name);

($w $h)

Notes #

• .^name (the type's name) is fully supported — see The type tower & introspection; .^parents gives the immediate superclasses.
• .isa tests strict class inheritance (5.isa(Numeric) is False, since Numeric is a role) — use ~~ for role/type membership.
• .^methods lists a type's methods; note it does not include the auto-generated bookkeeping methods (like POPULATE) that Rakudo also surfaces — the user-declared ones are all there.