How do I access JSON array data? - ruby

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.

Answer 1

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.

Answer 2

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" ]

Answer 3

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!