Feature #13601: Remove yield_self from Ruby 2.5 (already implemented)

• Status: Closed
• Assignee: -
• Target version: -

[danielpclark (Daniel P. Clark)]

Issue https://bugs.ruby-lang.org/issues/6721 for adding yield_self is unnecessary as BasicObject#instance_eval will do the exact same thing.

class BasicObject
  alias :yield_self :instance_eval
end

2.yield_self { |x| x*x } # => 4

I've tried all the examples of its given use cases and BasicObject#instance_eval will do them all.

In issue #6721 nobu said he didn't like the name yield_self. I'm in agreement about the name. Since BasicObject#instance_eval will already pipe in self and return the value of the block yield_self is not necessary.

[shan (Shannon Skipper)]

Note there are differences, for example

42.instance_eval { abs2 } #=> 1764

won't work with Kernel#yield_self and

42.yield_self #=> #<Enumerator: 42:yield_self>

won't work with BasicObject#instance_eval, etc.

[zverok (Victor Shepelev)]

instance_eval changes scope, while yield_self does not.

class A
  def foo
    1
  end

  def yield_self
    yield self
  end
end

def self.foo
  2
end

p A.new.instance_eval { self.foo * 3 } # => 3
p A.new.yield_self { self.foo * 3 } # => 6

An example is synthetic, yet the difference is important.
...and was discussed multiple times on the road to yield_self, to be honest.

[danielpclark (Daniel P. Clark)]

You both have provided better examples as to the differences. Also finding out yield_self returns an Enumerator was a new one to me. I guess this feature request can be closed.

[shyouhei (Shyouhei Urabe)]

• Status changed from Open to Closed

Closing as per request.