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 RubDoc and obviously Hash object doesn't have a to_json method. But I am reading blogs, that Rails supports active_record.to_json and it also supports hash#to_json. I can understand ActiveRecord is a Rails object, but Hash is not native to Rails, its 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.