Does not play well with DelegateClass

[msakrejda]

I ran into an issue where Oj is not serializing a DelegateClass as I expected. I was able to minimize the test case to something pretty simple:

require 'oj'
require 'json'

a = [1, 2, 3]

class MyArray < DelegateClass(Array); end

m = MyArray.new(a)

puts <<-EOF
JSON.generate:
       raw: #{JSON.generate(a)}
  delegate: #{JSON.generate(m)}

Oj.dump:
       raw: #{Oj.dump(a)}
  delegate: #{Oj.dump(m)}
EOF

the output is:

JSON.generate:
       raw: [1,2,3]
  delegate: [1,2,3]

Oj.dump:
       raw: [1,2,3]
  delegate: {"^o":"MyArray","delegate_dc_obj":[1,2,3]}

Is this expected? I expected Oj to behave like JSON.generate here. If this is intended, is there an option to mimic the JSON behavior? I looked through the docs but nothing stood out as relevant to me.

I ran into this working with Sequel's pg_array extension which wraps Array via DelegateClass.

[ohler55]

Oj is not replacement for the JSON gem by default. You have to use the :compat mode to make it act like the JSON gem. The default mode is object serialization mode. Take a look at the docs here http://ohler.com/oj/doc/file.Modes.html.

[msakrejda]

Thanks! After reading that doc (and the linked compat doc), I'm still not clear on the difference between mode: :compat and mimic_JSON, but mimic_JSON appears to resolve my issue.

[ohler55]

Compat mode is the same as the json gem output. With mimic you can make calls like JSON.dump and it will us Oj instead.