How to convert a ruby hash object to JSON?

Question

How to convert a ruby hash object to JSON? So I am trying this example below & it doesn't work?

I was looking at the RubyDoc and obviously Hash object doesn't have a to_json method. But I am reading on blogs that Rails supports active_record.to_json and also supports hash#to_json. I can understand ActiveRecord is a Rails object, but Hash is not native to Rails, it's a pure Ruby object. So in Rails you can do a hash.to_json, but not in pure Ruby??

car = {:make => "bmw", :year => "2003"} car.to_json 

Answer 1

One of the numerous niceties of Ruby is the possibility to extend existing classes with your own methods. That's called "class reopening" or monkey-patching (the meaning of the latter can vary, though).

So, take a look here:

car = {:make => "bmw", :year => "2003"} # => {:make=>"bmw", :year=>"2003"} car.to_json # NoMethodError: undefined method `to_json' for {:make=>"bmw", :year=>"2003"}:Hash #   from (irb):11 #   from /usr/bin/irb:12:in `<main>' require 'json' # => true car.to_json # => "{"make":"bmw","year":"2003"}" 

As you can see, requiring json has magically brought method to_json to our Hash.

Answer 2

require 'json/ext' # to use the C based extension instead of json/pure  puts {hash: 123}.to_json