Bug #2221: lib/delegate: freeze has odd effects

• Status: Closed
• Assignee: -
• Target version: 1.9.2
• ruby -v: ruby 1.9.2dev (2009-10-13 trunk 25317) [x86_64-darwin10.0.0]

[marcandre (Marc-Andre Lafortune)]

=begin
Freeze doesn't quite freeze, and can't be cloned:

require 'delegate'
d = SimpleDelegator.new([1,2,3])
d.freeze
d[0] = :hello; d # ==> [:hello, 2, 3], I expected a runtime error
d.clone # ==> RuntimeError, I expected some kind of copy of d

Maybe #freeze and #frozen should be forwarded:

diff --git a/lib/delegate.rb b/lib/delegate.rb
index 57c479c..f4bd453 100644
--- a/lib/delegate.rb
+++ b/lib/delegate.rb
@@ -115,7 +115,7 @@

implementation, see SimpleDelegator.

class Delegator

• [:to_s,:inspect,:=~,:!~,:===].each do |m|

• [:to_s,:inspect,:=~,:!~,:===, :freeze, :frozen?].each do |m|
  undef_method m
  end

But maybe the Delegator itself should also be frozen? I mean should a call to #setobj raise a runtime error or not?

Also, there are other methods that should probably be forwarded (eql?, hash, etc...); see issue #1333.
=end

[marcandre (Marc-Andre Lafortune)]

=begin
Hi,

On Fri, Oct 16, 2009 at 7:24 AM, Yukihiro Matsumoto [e-mail] wrote:

I think both should be frozen. I checked in the patch. I'd like to
see if it works (or not).

Indeed, I thought about it and came to the same conclusion when thinking of other non-trivial classes that would extend Delegate. It was too cold outside my bed though :-)

(a) Just to be sure: SimpleDelegator([1,2,3].freeze).frozen? should return false, right?

(b) Still can't clone it, though.
Is there a nice way to avoid the exception? The best I can think of is the inelegant:

diff --git a/lib/delegate.rb b/lib/delegate.rb
index 5d25632..5ef9c1c 100644
--- a/lib/delegate.rb
+++ b/lib/delegate.rb
@@ -188,11 +188,14 @@ class Delegator
setobj(obj)
end

• alias_method :original_dup, :dup
• private :original_dup

• Clone support for the object returned by __getobj__.

  def clone

• new = super

• new = frozen? ? original_dup : super
  new.setobj(getobj.clone)

• new

• frozen? ? new.freeze : new
  end
  # Duplication support for the object returned by __getobj__.
  def dup

=end

[matz (Yukihiro Matsumoto)]

=begin
Hi,

In message "Re: [ruby-core:26118] [Bug #2221] lib/delegate: freeze has odd effects"
on Fri, 16 Oct 2009 15:43:40 +0900, Marc-Andre Lafortune [e-mail] writes:

|Freeze doesn't quite freeze, and can't be cloned:

|But maybe the Delegator itself should also be frozen? I mean should a call to #setobj raise a runtime error or not?

I think both should be frozen. I checked in the patch. I'd like to
see if it works (or not).

|Also, there are other methods that should probably be forwarded (eql?, hash, etc...); see issue #1333.

I have tried once, but code became vary clumsy, mostly because no
constant can be accessed or initialized from BasicObject.

						matz.

=end

[mame (Yusuke Endoh)]

• Status changed from Open to Closed

=begin
Hi,

This ticket was duplicated by #2679.
After that, lib/delegate.rb has been changed bit by bit.
As a result of matz and nobu's effort, this seems to work now.

--
Yusuke Endoh [e-mail]
=end