Array#to_s in Ruby 2.1 broke my code

Question

This code broke on Ruby 2.1

class Test
  def to_s()
    "hi"
  end
end

puts [Test.new(), Test.new()].to_s

Ruby 1.9.3:

$ ruby --version
ruby 1.9.3p484 (2013-11-22 revision 43786) [x86_64-linux]
$ /opt/chef/embedded/bin/ruby test.rb
[hi, hi]

Ruby 2.1:

$ ruby --version
ruby 2.1.4p265 (2014-10-27 revision 48166) [x86_64-linux]
$ ruby test.rb
[#<Test:0x000000022ac400>, #<Test:0x000000022ac3d8>]

Is this documented somewhere? How can the old behavior be preserved?

As per documentation http://www.ruby-doc.org/core-2.1.1/Object.html#method-i-to_s it states that it will return object's class encoding object's Id. — user944938, Dec 17 '14 at 19:09
Same as in here: http://www.ruby-doc.org/core-1.9.3/Object.html#method-i-to_s — omribahumi, Dec 17 '14 at 19:14
@user944938 but the OP is providing his own implementation of to_s() — Hector Correa, Dec 17 '14 at 19:16
Here is it: "Ruby 2.0 uses #to_s as an alias to #inspect" https://bugs.ruby-lang.org/issues/8520 (straight from Yukihiro Matsumoto) — Hector Correa, Dec 17 '14 at 19:21

the Tin Man · Accepted Answer · 2014-12-17T19:28:33.127

5

Your code:

puts [Test.new(), Test.new()].to_s

is a questionable use of Array.to_s. Instead I'd use:

puts [Test.new(), Test.new()].map(&:to_s)

While I can see that the first use makes sense, the second use makes more sense and should work in any version of Ruby.

edited Dec 17 '14 at 19:28

answered Dec 17 '14 at 19:22

the Tin Man

I figured there's a way around this, I guess there isn't. Thanks – omribahumi Dec 17 '14 at 19:30
1

I agree with this. When you want to call a method on an object inside an Enumerable I think you should have to enter into the Object and call the method internally using something like `map` in this case. I think the original implementation is a little less in congruence with OO design than the 2.0 version. – engineersmnky Dec 17 '14 at 19:30
1

Also just as a note `map(&:to_s)` is actually faster than `Array#to_s` by more than a marginal amount. Although this simple implementation is inconsequential mass implementation could show as much as 60% difference in performance. Althouhg please note the difference in out put `Array#to_s` in this case will be `"[hi,hi]"` where as `map(&:to_s)` will be `["hi","hi"]` – engineersmnky Dec 17 '14 at 20:16

score 1 · Answer 2 · answered Dec 17 '14 at 19:16

1

On ruby 2.1.5:

class Test
  def to_s
    "hi"
  end

  alias inspect to_s # add this line
end

puts [Test.new, Test.new].to_s
#=> [hi, hi]

This seems like a bug to me. If it is intended behavior, that is really annoying.

answered Dec 17 '14 at 19:16

Adrian

I don't want to override inspect. I use it for a different purpose. – omribahumi Dec 17 '14 at 19:18

Max · Answer 3 · 2014-12-17T22:03:54.560

0

You don't need to_s. puts does the work for you

puts [Test.new(), Test.new()]
# hi
# hi

If you want the brackets, that's what inspect is for (in which case it makes sense that you would need to define Test#inspect).

edited Dec 17 '14 at 22:03

answered Dec 17 '14 at 21:58

Max

3 Answers3