Ruby BasicObject方法

Question

while going through Ruby, i encountered that BasicObject is the top most superclass of Class. When I tried BasicObject.methods , i get list of these methods

[:method_missing, :singleton_method_added, :singleton_method_undefined, :singleton_method_removed, :new, :become_java!, :allocate, :superclass, :java_class, :class_variables, :<=, :public_instance_methods, :prepend, :class_variable_get, :public_constant, :singleton_class?, :instance_methods, :freeze, :instance_method, :const_defined?, :to_s, :constants, :ancestors, :private_instance_methods, :===, :included_modules, :==, :using, :class_eval, :const_get, :refine, :protected_instance_methods, :public_instance_method, :class_variable_defined?, :inspect, :name, :private_constant, :<, :hash, :>, :>=, :module_exec, :protected_method_defined?, :module_eval, :const_missing, :class_exec, :const_set, :private_method_defined?, :public_class_method, :autoload, :<=>, :include, :public_method_defined?, :autoload?, :class_variable_set, :include?, :remove_class_variable, :deprecate_constant, :private_class_method, :method_defined?, :include_class, :handle_different_imports, :java_kind_of?, :public_send, :frozen?, :protected_methods, :java_implements, :public_method, :java, :singleton_methods, :untaint, :javafx, :enum_for, :private_methods, :method, :instance_variables, :object_id, :extend, :itself, :instance_variable_set, :respond_to?, :java_name, :methods, :to_java, :java_package, :singleton_class, :public_methods, :to_enum, :display, :tainted?, :instance_variable_defined?, :untrusted?, :define_singleton_method, :!~, :nil?, :com, :instance_of?, :java_require, :javax, :java_signature, :tap, :java_annotation, :send, :trust, :instance_variable_get, :is_a?, :eql?, :java_field, :remove_instance_variable, :untrust, :class, :=~, :org, :taint, :kind_of?, :clone, :dup, :!, :equal?, :instance_exec, :__id__, :instance_eval, :__send__, :!=]

(I have Jruby present as well so some extra methods)

But when I call BasicObject.methods(false) (false parameter for displaying methods of the same class itself), I get

=> [:method_missing, :singleton_method_added, :singleton_method_undefined, :singleton_method_removed]

I have a query, ideally class.methods with false param should return only its methods and BasicObject.superclass returns nil. Is there any other hierarchy? from where does these methods coming from.

I'm learning Ruby Apologozies if i'm missing something. Thanks

Answer 1

Those methods are indeed defined on BasicObject, though they are mostly just empty definitions ( method_missing actually does some work). Check the source .

I can't say exactly why, but there could be a hint in the comments:

Some care has been taken to make the implementation be as monomorphic as possible, so that the Java Hotspot engine can improve performance of it. That is the reason for several patterns that might seem odd in this class.

Those methods are all common hooks that are redefined for metaprogramming purposes. By defining them on BasicObject, it could be that this allows for much faster method resolution by simplifying the inheritance chain.

Answer 2

You are not asking what instance methods are defined on BasicObject , that would be BasicObject.instance_methods . You are asking, what methods you can call on BasicObject . Well, BasicObject is an object just like any other object, so you can call any method on it that is defined in its class (which in this case is Class ) or in the superclasses of its class (which in this case are Module , Object , Kernel , and BasicObject ).