Metaobject that supports storing and introspecting methods
role Metamodel::MethodContainer {}
Warning: this role is part of the Rakudo implementation, and is not a part of the language specification.
Roles, classes, grammars and enums can contain methods. This role implements the API around storing and introspecting them.
say .name for Int.^methods(:all);
# don't do that, because it changes type Int globally.
# just for demonstration purposes.
Int.^add_method('double', method ($x:) { 2 * $x });
say 21.double; # OUTPUT: «42»
method add_method($obj, $name, $code)
Adds a method to the metaclass, to be called with name $name. This should only be done before a type is composed.
method methods($obj, :$all, :$local)
Returns a list of public methods available on the class (which includes methods from superclasses and roles). By default this stops at the classes Cool, Any or Mu; to really get all methods, use the :all adverb. If :local is set, only methods declared directly in the class are returned.
class A {
method x() { };
}
say A.^methods(); # x
say A.^methods(:all); # x infinite defined ...
The returned list contains objects of type Method, which you can use to introspect their signatures and call them.
Some introspection method-look-alikes like WHAT will not show up, although they are present in any Raku object. They are handled at the grammar level and will likely remain so for bootstrap reasons.
method method_table($obj --> Hash:D)
Returns a hash where the keys are method names, and the values are Methods. Note that the keys are the names by which the methods can be called, not necessarily the names by which the methods know themselves.
method lookup($obj, $name --> Method)
Returns the first matching Method object of the provided $name or (Mu) if no method object was found. The search for a matching method object is done by following the mro of $obj. Note that lookup is supposed to be used for introspection, if you're after something which can be invoked you probably want to use find_method instead.
say 2.5.^lookup("sqrt").raku; # OUTPUT: «method sqrt (Rat $: *%_) ...»
say Str.^lookup("BUILD").raku; # OUTPUT: «submethod BUILD (Str $: :$value = "", *%_ --> Nil) ...»
say Int.^lookup("does-not-exist"); # OUTPUT: «(Mu)»
The difference between find_method and lookup are that find_method will use a default candidate for parametric roles, whereas lookup throws an exception in this case, and that find_method honors FALLBACK methods, which lookup does not.