What is the usage of `retry` on Ruby 1.9?

Question

In Ruby 1.8, retry can be use like:

for i in 0..4
  puts i
  retry if i == 4
end

but in Ruby 1.9, it throw an error: Invalid retry, what is the usage of retry in Ruby 1.9? I can't find retry on http://www.ruby-doc.org =(

Why not try searching for `ruby + retry`? All sorts of hits come up on Google, which show the syntax for using it. — the Tin Man, Feb 19 '13 at 07:35
Possible duplicate of http://stackoverflow.com/questions/10063166/what-is-the-purpose-of-redo-and-retry-statements-in-ruby/10064392#10064392 — the Tin Man, Feb 19 '13 at 07:37

score 6 · Answer 1 · answered Feb 19 '13 at 07:00

6

It is for retrying failed operations (when you catch an exception)

n = 0
begin
  puts 'Trying to do something'
  raise 'oops'
rescue => ex
  puts ex
  n += 1
  retry if n < 3
end
puts "Ok, I give up"


# >> Trying to do something
# >> oops
# >> Trying to do something
# >> oops
# >> Trying to do something
# >> oops
# >> Ok, I give up

answered Feb 19 '13 at 07:00

Sergio Tulentsev

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Where I can find the reference from official? =) – Steely Wing Feb 19 '13 at 07:06
@WingLeong http://www.ruby-doc.org/docs/ProgrammingRuby/html/tut_expressions.html#UM – oldergod Feb 19 '13 at 07:13
1

Thanks, but this doc doesn't show how to use `retry` in rescue. =S – Steely Wing Feb 19 '13 at 07:17

l__flex__l · Answer 2 · 2014-08-18T13:14:42.950

Firstly, i believe retry would only work in a begin end block (or implicit begin end block in a method definition). Meaning it would jump back to begin. Not the beginning of a loop. Also as of 1.9 retry only works in a rescue.

begin # should jump here
  for i in 4..0
    puts i
    4 / i
  end
rescue
  retry
end

I think what you are looking for is redo.

for i in 0..4
  puts i
  redo if i == 4
end

Be aware that redo will perform the last iteration again. Results being:

0
1
2
3
4
4 # => infinite loop

score 0 · Answer 3 · answered Dec 20 '16 at 22:04

Ruby 1.9 supports retry in begin rescue clauses only.

You can use a continuation to replicate the behavior of the old retry

require 'continuation'

def with_retry
  loop { callcc { |cc| def cc.retry; call; end; yield cc; return }}
end

with_retry do |cc|
  for n in 1..4
    puts n
    cc.retry if n == 4
  end
end

What is the usage of `retry` on Ruby 1.9?

3 Answers3