Feature #2451

BasicObject.initialize with variable number of argument

Added by marcandre (Marc-Andre Lafortune) almost 11 years ago. Updated over 9 years ago.

Target version:


If one wants to write a class easily extensible (for some kind of library, say), then there is no nice way to have the initialize method be extensible other than through monkeypatching.

This could be made much more flexible if BasicObject.initialize accepted any number of arguments.

Would there be a downsize to have BasicObject.initialize accept many arguments?

Here's a more detailed example:

class NiceClass
def initialize(arg1, arg2)
# do some stuff with arg1 and arg2
super # allow for included modules to initialize

# Someone else:
class NiceClass
module CoolExtension
def initialize(arg1, arg2)
# do cool stuff
super # allow for more extensions

include CoolExtension

This would not work unless BasicObject#initialize accepts any number of arguments. Currently, only super() -- i.e. passing none of the arguments -- can be called, so arg1 & arg2 must be copied to instance variables for included modules to access, or else monkeypatching becomes the only possibility.

The patch is trivial:

diff --git a/object.c b/object.c
index 10eb983..33cae20 100644
--- a/object.c
+++ b/object.c
@@ -2538,7 +2538,7 @@ Init_Object(void)
#undef rb_intern
#define rb_intern(str) rb_intern_const(str)

  • rb_define_private_method(rb_cBasicObject, "initialize", rb_obj_dummy, 0);
  • rb_define_private_method(rb_cBasicObject, "initialize", rb_obj_dummy, -1); rb_define_alloc_func(rb_cBasicObject, rb_class_allocate_instance); rb_define_method(rb_cBasicObject, "==", rb_obj_equal, 1); rb_define_method(rb_cBasicObject, "equal?", rb_obj_equal, 1);


  • There is no documentation for BasicObject#initialize.
  • Ironically, the Ruby Draft Specification states that Object#initialize accepts any number of arguments! I'm glad I already have that team agree with me ;-)
  • No error is generated by make test-all
  • See also where Robert Klemme recommends calling super from constructors but has to use super(), i.e. passing no arguments

Similarly, I also propose that Object#initialize accepts any number of arguments in Ruby 1.8.8

Related issues

Related to Ruby master - Bug #5542: Ruby 1.9.3-p0 changed arity on default initialization methodRejectedmarcandre (Marc-Andre Lafortune)11/02/2011Actions

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