Issue #12084 has been updated by Colin Fulton.


This feature would solve a lot of problems I had while doing what should have been simple meta-programming (if there is such a thing as "simple" meta-programming...).

Something to consider is what happens with nested singleton classes. Let's say you have this code:

```ruby
Array.singleton_class
     .singleton_class
     .instance
```

Does that return `Array` or the first singleton class? I would think the former is more useful, but less obvious.

----------------------------------------
Feature #12084: `Class#instance`
https://bugs.ruby-lang.org/issues/12084#change-57384

* Author: Tsuyoshi Sawada
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------
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
~~~



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