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
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](https://stackoverflow.com/questions/394144/what-does-monkey-patching- exactly-mean-in-ruby), 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.
