Tweaking Hash#to_json

Question

Hi guys,

I've been struggling with this one the whole day. In my Rails 2.3.5 app, I had a bunch of custom code which allowed the following to happen:

>> strip_hash_keys_for_json({ "a" => 1 }).to_json
=> "{ a: 1 }"

So you see that string keys don't get quoted. It was implemented by creating a String descendant class that returned self from to_json, and all of the hash keys were wrapped in this class.

Today I've started upgrading the app to Rails 3, and it has stopped working, since the JSON-encoding stuff had been rewritten quite seriously.

As you may probably know, in Rails 3 creating a JSON representation of a hash involves two methods:

• as_json which determines what elements of the hash should be present in JSON
• encode_json which actually returns a string representation containing the JSON

I figured that I can change the way things happen by observing what encode_json does, and tweaking some methods that get called from there.

The problem is that these two methods don't get called at all. I've checked for every stupid mistake I could make in my investigations and I can see nothing wrong. Google is of no help too, so I turn to the SO fellows for assistance.

Thanks a lot.

UPDATE

OK so I figured out that in order for these methods to work I have to use ActiveSupport::JSON::encode directly instead of to_json. This seems weird because I thought {}.to_json is handled by the Object#to_json method defined in that same encoding.rb file, which in turn calls ActiveSupport::JSON.encode(self, options).

Now I'm totally confused.

Answer 1

What happens when you remove the strip_hash_keys_for_json ?

I opened up a console and got:

ruby-1.8.7-p249 > Rails::VERSION::STRING
 => "2.3.5"
ruby-1.8.7-p249 > { "a" => 1 }.to_json
 => "{\"a\":1}"