CODEWITHSUNDEEP
crubymarshallingalias
Strelokhalfer
Strelokhalfer

Reputation: 344

Alias module`s method in C(Ruby Extension)

I can`t alias method "dump" from Marshal module

#include "ruby.h"
VALUE Marshal = Qnil;
void Init_test(){
  Marshal = rb_define_module("Marshal");
  rb_define_alias(Marshal, "hal_dump", "dump");//No error, but don`t work
}

In ruby:

require './test'
p Marshal.methods.grep(/dump/).sort #[:dump]

How i can do alias?

Upvotes: 2

Views: 89

Answers (1)

cremno
cremno

Reputation: 4927

Your C code is similar to the following Ruby code:

module Marshal
  alias hal_dump dump
end

dump is a singleton method but also a private instance method (that combination is a so-called module function). You only define an alias of the private instance method.

p Marshal.private_instance_methods.grep(/dump/) # => [:dump, :hal_dump]

That's also why you don't get an error. However you want to define an alias of the singleton method. That can be done by opening the singleton class. A corrected Ruby version might look like this:

p Marshal.methods.grep(/dump/) # => [:dump]
class << Marshal
  alias hal_dump dump
end
p Marshal.methods.grep(/dump/) # => [:dump, :hal_dump]

The MRI C API implements the rb_singleton_class() function. It returns the singleton class and can be used like this to fix your code:

rb_define_alias(rb_singleton_class(Marshal), "hal_dump", "dump");

Upvotes: 4

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