user310525 user310525 - 3 months ago 9
JSON Question

How to convert a ruby hash object to JSON?

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, 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.

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