How do I access JSON array data?

Question

I have the following array:

[ { "attributes": {
      "id":   "usdeur",
      "code": 4
    },
    "name": "USD/EUR"
  },
  { "attributes": {
      "id":   "eurgbp",
      "code": 5
    },
    "name": "EUR/GBP"
  }
]

How can I get both ids for futher processing as output?

I tried a lot but no success. My problem is I always get only one id as output:

Market.all.select.each do |market|
  present market.id
end

Or:

Market.all.each{|attributes| present attributes[:id]}

which gives me only "eurgbp" as a result while I need both ids.

Unless you convert your keys to symbols, JSON structures are strings and strings only for keys. — tadman
– tadman, Commented Sep 8, 2014 at 15:39

engineersmnky · Accepted Answer · 2014-09-08 15:40:14Z

2

JSON#parse should help you with this

require 'json'

json = '[ { "attributes": {
             "id":   "usdeur",
             "code": 4
           },
            "name": "USD/EUR"
           },
         { "attributes": {
            "id":   "eurgbp",
            "code": 5
           },
           "name": "EUR/GBP"
         }]'

ids = JSON.parse(json).map{|hash| hash['attributes']['id'] }
#=> ["usdeur", "eurgbp"]

JSON#parse turns a jSON response into a Hash then just use standard Hash methods for access.

answered Sep 8, 2014 at 15:40

engineersmnky

30.5k2 gold badges42 silver badges64 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Jordan Running · Accepted Answer · 2014-09-08 15:41:39Z

I'm going to assume that the data is JSON that you're parsing (with JSON.parse) into a Ruby Array of Hashes, which would look like this:

hashes = [ { "attributes" => { "id" => "usdeur", "code" => 4 },
             "name"       => "USD/EUR"
           },
           { "attributes" => { "id" => "eurgbp", "code" => 5 },
             "name"       => "EUR/GBP"
           } ]

If you wanted to get just the first "id" value, you'd do this:

first_hash = hashes[0]
first_hash_attributes = first_hash["attributes"]
p first_hash_attributes["id"]
# => "usdeur"

Or just:

p hashes[0]["attributes"]["id"]
# => "usdeur"

To get them all, you'll do this:

all_attributes = hashes.map {|hash| hash["attributes"] }
# => [ { "id" => "usdeur", "code" => 4 },
#      { "id" => "eurgbp", "code" => 5 } ]

all_ids = all_attributes.map {|attrs| attrs["id"] }
# => [ "usdeur", "eurgbp" ]

Or just:

p hashes.map {|hash| hash["attributes"]["id"] }
# => [ "usdeur", "eurgbp" ]

Oleh Sobchuk · Accepted Answer · 2014-09-08 18:39:52Z

0

JSON library what using Rails is very slowly...

I prefer to use:

gem 'oj'

from https://github.com/ohler55/oj

fast and simple! LET'S GO!

answered Sep 8, 2014 at 18:39

Oleh Sobchuk

3,7222 gold badges31 silver badges45 bronze badges

Collectives™ on Stack Overflow

How do I access JSON array data?

3 Answers 3

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related