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

Ruby's bundled JSON is capable of exhibiting a bit of magic on its own.

If you have a string containing JSON serialized data that you want to parse:

JSON[string_to_parse]

JSON will look at the parameter, see it's a String and try decoding it.

Similarly, if you have a hash or array you want serialized, use:

JSON[array_of_values]

Or:

JSON[hash_of_values]

And JSON will serialize it. You can also use the to_json method if you want to avoid the visual similarity of the [] method.

Here are some examples:

hash_of_values = {'foo' => 1, 'bar' => 2}
array_of_values = [hash_of_values]

JSON[hash_of_values] 
# => "{\"foo\":1,\"bar\":2}"

JSON[array_of_values] 
# => "[{\"foo\":1,\"bar\":2}]"

string_to_parse = array_of_values.to_json
JSON[string_to_parse]
# => [{"foo"=>1, "bar"=>2}]

If you root around in JSON you might notice it's a subset of YAML, and, actually the YAML parser is what's handling JSON. You can do this too:

require 'yaml'

YAML.load(string_to_parse)
# => [{"foo"=>1, "bar"=>2}]

If your app is parsing both YAML and JSON, you can let YAML handle both flavors of serialized data.