[ruby-core:106577] [Ruby master Feature#12084] `Class#instance`

Issue #12084 has been updated by matz (Yukihiro Matsumoto).


* `instance` is NG. For example, `Array.instance => nil` is confusing
* `attached_object` is better, at least for singleton classes. But there's still no real-world use-case.

For your information, `NilClass` is not a singleton class. It's a class with only an instance. This is side evidence of this method is confusing. Even the original proposer can misunderstand the concept.

Matz.


----------------------------------------
Feature #12084: `Class#instance`
https://bugs.ruby-lang.org/issues/12084#change-95240

* Author: sawa (Tsuyoshi Sawada)
* Status: Open
* Priority: Normal
----------------------------------------
For meta-programming/debugging purposes, I would like to request the inverse of `Object#singleton_class`. Namely, a method that is called on a class that is a singleton class, and returns the object it is a singleton of. Since the `Singleton` module in the standard library http://ruby-doc.org/stdlib-2.3.0/libdoc/singleton/rdoc/Singleton.html assigns the method name `instance` to such classes, I think `Class#instance` should be the name for such feature.

~~~RUBY
Array.singleton_class.instance # => Array
"foo".singleton_class.instance # => "foo"
~~~

When the receiver is a class but is not a singleton class, then it should raise an error.

~~~RUBY
Array.instance # => error
~~~



-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:[e-mail]?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>