From: "mame (Yusuke Endoh) via ruby-core" <ruby-core@...>
Date: 2023-04-14T01:10:50+00:00
Subject: [ruby-core:113231] [Ruby master Feature#19561] ObjectSpace::WeakMap#delete and ObjectSpace::WeakKeyMap#delete

Issue #19561 has been updated by mame (Yusuke Endoh).


Discussed at the dev meeting. @matz accepted this.

----------------------------------------
Feature #19561: ObjectSpace::WeakMap#delete and ObjectSpace::WeakKeyMap#delete
https://bugs.ruby-lang.org/issues/19561#change-102778

* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
----------------------------------------
I just realized in https://bugs.ruby-lang.org/issues/19560#Ruby-shim that there's no way to remove elements from either WeakMaps.

I think they could both benefit from a `delete` method.

### Use case

For example, to keep track of a subset of instances of a class, you may need to remove some from the list when a condition changes:

```ruby
class Connection
  CLOSE_ON_FORK = ObjectSpace::WeakMap.new

  class << self
    def after_fork
      CLOSE_ON_FORK.each_key do |connection|
        connection.close if connection.close_on_fork?
      end
    end
  end

  def close_on_fork=(enabled)
    if enabled
      CLOSE_ON_FORK[self] = true
    else
      CLOSE_ON_FORK.delete(self)
    end
    @close_on_fork = enabled
  end

  def close_on_fork?
    @close_on_fork
  end
end

module CloseOnFork
  IOS = ObjectSpace::WeakMap.new

  def _fork
    pid = super
    if pid == 0 # child
      ::Connection.after_fork
    end
    pid
  end
end
Process.singleton_class.prepend(CloseIOOnFork)
```




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