JSON Serialization in Ruby

While working on my review of [Text Provessing in Ruby]TPiR, I encountered a module required that I hadn’t seen before:

require 'json'
require 'json/add/core'

The code was writing to and reading from a JSON string being generated from a Struct - and the it failed when the second require wasn’t there.

I couldn’t find anything in the [Ruby Docs][] when I looked (failure of search skills no doubt), but I was able to find the [original GitHub repo][JSONgh] where the JSON module was created

Digging through the file structure src/json/add/core, I could see that [core.rb] required all the other files in /add. And that those files were monkey patching a number of the core Ruby classes with new to_json and json_create methods. Exciting stuff.

Reading a little further along in the Readme, it became apparent that these methods were being used as a way of serializing a those core classes as JSON. Let me try to explain by taking a look at the patched methods on the Regexp class.

The docs say: > It’s possible to add JSON support serialization to arbitrary classes > by simply implementing a more specialized version of the #to_json > method, that should return a JSON object.

And we can see that to_json method (called slightly indirectly) here:

  def as_json(*)
    {
      JSON.create_id => self.class.name,
      'o'            => options,
      's'            => source,
    }
  end

  def to_json(*)
    as_json.to_json
  end

Here the json produced from to_json has three properties = JSON.create_id

The (*) is just soaking up (and ignoring) any arguments sent to both of the