How do I parse JSON with Ruby on Rails? [duplicate

Question

This question already has an answer here:

• Parsing a JSON string in Ruby 7 answers

I'm looking for a simple way to parse JSON, extract a value and write it into a database in Rails.

Specifically what I'm looking for, is a way to extract shortUrl from the JSON returned from the bit.ly API:

{
  "errorCode": 0,
  "errorMessage": "",
  "results":
  {
    "http://www.foo.com":
    {
       "hash": "e5TEd",
       "shortKeywordUrl": "",
       "shortUrl": "http://bit.ly/1a0p8G",
       "userHash": "1a0p8G"
    }
  },
  "statusCode": "OK"
}

And then take that shortUrl and write it into an ActiveRecord object associated with the long URL.

This is one of those things that I can think through entirely in concept and when I sit down to execute I realize I've got a lot to learn.

Answer 1

This can be done as below, just need to use JSON.parse, then you can traverse through it normally with indices.

#ideally not really needed, but in case if JSON.parse is not identifiable in your module  
require 'json'

#Assuming data from bitly api is stored in json_data here

json_data = '{
  "errorCode": 0,
  "errorMessage": "",
  "results":
  {
    "http://www.foo.com":
    {
       "hash": "e5TEd",
       "shortKeywordUrl": "",
       "shortUrl": "http://whateverurl",
       "userHash": "1a0p8G"
    }
  },
  "statusCode": "OK"
}'

final_data = JSON.parse(json_data)
puts final_data["results"]["http://www.foo.com"]["shortUrl"]

Answer 2

You can try something like this:

def details_to_json
{
  :id                    => self.id, 
  :credit_period_type    => self.credit_period_type,
  :credit_payment_period => self.credit_payment_period,

 }.to_json
end

Answer 3

Here is an update for 2013.

Ruby

Ruby 1.9 has a default JSON gem with C extensions. You can use it with

require 'json'
JSON.parse ''{ "x": "y" }'
# => {"x"=>"y"}

The parse! variant can be used for safe sources. There are also other gems, which may be faster than the default implementation. Please refer to multi_json for the list.

Rails

Modern versions of Rails use multi_json, a gem that automatically uses the fastest JSON gem available. Thus, the recommended way is to use

object = ActiveSupport::JSON.decode json_string

Please refer to ActiveSupport::JSON for more information. In particular, the important line in the method source is

data = MultiJson.load(json, options)

Then in your Gemfile, include the gems you want to use. For example,

group :production do
  gem 'oj'
end

Answer 4

require 'json'
out=JSON.parse(input)

This will return a Hash

Answer 5

The Oj gem (https://github.com/ohler55/oj) should work. It's simple and fast.

http://www.ohler.com/oj/#Simple_JSON_Writing_and_Parsing_Example

require 'oj'

h = { 'one' => 1, 'array' => [ true, false ] }
json = Oj.dump(h)

# json =
# {
#   "one":1,
#   "array":[
#     true,
#     false
#   ]
# }

h2 = Oj.load(json)
puts "Same? #{h == h2}"
# true

The Oj gem won't work for JRuby. For JRuby this (https://github.com/ralfstx/minimal-json) or this (https://github.com/clojure/data.json) may be good options.

Answer 6

This answer is quite old. pguardiario's got it.

One site to check out is JSON implementation for Ruby. This site offers a gem you can install for a much faster C extension variant.

With the benchmarks given their documentation page they claim that it is 21.500x faster than ActiveSupport::JSON.decode

The code would be the same as Milan Novota's answer with this gem, but the parsing would just be:

parsed_json = JSON(your_json_string)