Rails serialization of Range of integers is broken - ruby-on-rails

Question

I need to serialize ruby Ranges using YAML, in a rails context.
I wanted to check if ranges of integers and ranges of strings were serialized properly.
Here was my test:
# classic irb
require 'yaml' # => true
YAML::VERSION # => "0.60"
YAML.dump(1..2) # => "--- !ruby/range \nbegin: 1\nend: 2\nexcl: false\n"
YAML.dump("1".."2") # => "--- !ruby/range \nbegin: \"1\"\nend: \"2\"\nexcl: false\n"
The two outputs are dutifully distinct, so I got forward and coded it inside my rails application.
However it seems that within a rails context, ruby forgets how to properly serialize a range of integers!
# ./script/rails console
Rails::VERSION::STRING # => "3.0.15"
RUBY_VERSION # => "1.8.7"
YAML::VERSION # => "0.60"
YAML.dump(1..2) # => "--- !ruby/range\n begin: 1\n end: 2\n excl: false"
YAML.dump("1".."2") # => "--- !ruby/range\n begin: 1\n end: 2\n excl: false"
# The two outputs are identical, the distinction between integers and strings is lost!
Both ruby and ruby on rails seem to use the same version of the YAML library.
If I don't get it wrong, my version of ruby doesn't support switching between multiple coder engines.
I have a few questions:
What is the cause of this difference?
Does this problem arise with newer versions of ruby / rails?
How could I fix that properly, in a compatible manner?
Thank you for your help.

Answer 1

A range is a Ruby internal, not a YAML base type like an integer or string. Rather than encode the range as you are, use its start and end points and reconstruct the range on the receiving end.
I use something like:
[1] (pry) main: 0> range = 0..1
=> 0..1
[2] (pry) main: 0> require 'yaml'
=> true
[3] (pry) main: 0> YAML.dump(range)
=> "--- !ruby/range\nbegin: 0\nend: 1\nexcl: false\n"
[4] (pry) main: 0> YAML.dump({'min' => range.min, 'max' => range.max})
=> "---\nmin: 0\nmax: 1\n"
And then I can recreate the range on the receiving side using something like:
Range.new(*YAML.load(YAML.dump({'min' => range.min, 'max' => range.max})).values)
=> 0..1
or this if you're not sure that 'min' and 'max' will be in the right order:
[19] (pry) main: 0> Range.new(*YAML.load(YAML.dump({'min' => range.min, 'max' => range.max})).values_at('min', 'max'))
=> 0..1
Adding some information regarding Ruby 1.9.3+ serializing ranges of characters:
[2] (pry) main: 0> range = '0'..'1'
=> "0".."1"
[3] (pry) main: 0> YAML.dump(range)
=> "--- !ruby/range\nbegin: '0'\nend: '1'\nexcl: false\n"
[5] (pry) main: 0> RUBY_VERSION
=> "1.9.3"
And again with 1.9.2+:
[2] (pry) main: 0> range = '0'..'1'
=> "0".."1"
[3] (pry) main: 0> YAML.dump(range)
=> "--- !ruby/range \nbegin: \"0\"\nend: \"1\"\nexcl: false\n"
[4] (pry) main: 0> RUBY_VERSION
=> "1.9.2"
And, the workaround maintains the range start/end types:
[6] (pry) main: 0> Range.new(*YAML.load(YAML.dump({'min' => range.min, 'max' => range.max})).values_at('min', 'max'))
=> "0".."1"
In both cases the YAML_VERSION is 0.60.