Parsing a JSON string in Ruby

问题:

I have a string that I want to parse in Ruby:

string = \'{\"desc\":{\"someKey\":\"someValue\",\"anotherKey\":\"value\"},\"main_item\":{\"stats\":{\"a\":8,\"b\":12,\"c\":10}}}\'

Is there an easy way to extract the data?

回答1:

This looks like JavaScript Object Notation (JSON). You can parse JSON that resides in some variable, e.g. json_string, like so:

require \'json\'
JSON.parse(json_string)

If you’re using an older Ruby, you may need to install the json gem.

---

There are also other implementations of JSON for Ruby that may fit some use-cases better:

• YAJL C Bindings for Ruby
• JSON::Stream

回答2:

Just to extend the answers a bit with what to do with the parsed object:

# JSON Parsing example
require \"rubygems\"
require \"json\"

string = \'{\"desc\":{\"someKey\":\"someValue\",\"anotherKey\":\"value\"},\"main_item\":{\"stats\":{\"a\":8,\"b\":12,\"c\":10}}}\'
parsed = JSON.parse(string) # returns a hash

p parsed[\"desc\"][\"someKey\"]
p parsed[\"main_item\"][\"stats\"][\"a\"]

# Read JSON from a file, iterate over objects
file = open(\"shops.json\")
json = file.read

parsed = JSON.parse(json)

parsed[\"shop\"].each do |shop|
  p shop[\"id\"]
end

回答3:

As of Ruby v1.9.3 you don\'t need to install any Gems in order to parse JSON, simply use require \'json\':

require \'json\'

json = JSON.parse \'{\"foo\":\"bar\", \"ping\":\"pong\"}\'
puts json[\'foo\'] # prints \"bar\"

See JSON at Ruby-Doc.

回答4:

It looks like a JSON string. You can use one of many JSON libraries and it\'s as simple as doing:

JSON.parse(string)

回答5:

This is a bit late but I ran into something interesting that seems important to contribute.

I accidentally wrote this code, and it seems to work:

require \'yaml\'
CONFIG_FILE = ENV[\'CONFIG_FILE\'] # path to a JSON config file 
configs = YAML.load_file(\"#{CONFIG_FILE}\")
puts configs[\'desc\'][\'someKey\']

I was surprised to see it works since I am using the YAML library, but it works.

The reason why it is important is that yaml comes built-in with Ruby so there\'s no gem install.

I am using versions 1.8.x and 1.9.x - so the json library is not built in, but it is in version 2.x.

So technically - this is the easiest way to extract the data in version lower than 2.0.

回答6:

That data looks like it is in JSON format.

You can use this JSON implementation for Ruby to extract it.

回答7:

I suggest Oj as it is waaaaaay faster than the standard JSON library.

https://github.com/ohler55/oj

(see performance comparisons here)