How to convert a Ruby object to JSON

Question

I would like to do something like this:

require 'json'  class Person attr_accessor :fname, :lname end  p = Person.new p.fname = "Mike" p.lname = "Smith"  p.to_json 

Is it possible?

Answer 1

Yes, you can do it with to_json.

You may need to require 'json' if you're not running Rails.

Answer 2

To make your Ruby class JSON-friendly without touching Rails, you'd define two methods:

• to_json, which returns a JSON object
• as_json, which returns a hash representation of the object

When your object responds properly to both to_json and as_json, it can behave properly even when it is nested deep inside other standard classes like Array and/or Hash:

#!/usr/bin/env ruby  require 'json'  class Person      attr_accessor :fname, :lname      def as_json(options={})         {             fname: @fname,             lname: @lname         }     end      def to_json(*options)         as_json(*options).to_json(*options)     end  end  p = Person.new p.fname = "Mike" p.lname = "Smith"  # case 1 puts p.to_json                  # output: {"fname":"Mike","lname":"Smith"}  # case 2 puts [p].to_json                # output: [{"fname":"Mike","lname":"Smith"}]  # case 3 h = {:some_key => p} puts h.to_json                  # output: {"some_key":{"fname":"Mike","lname":"Smith"}}  puts JSON.pretty_generate(h)    # output                                 # {                                 #   "some_key": {                                 #     "fname": "Mike",                                 #     "lname": "Smith"                                 #   }                                 # } 

Also see "Using custom to_json method in nested objects".