Ruby - Extract array from nested array of hashes

Question

I'm trying to obtain a hash from the following:

 response: 
 {"result": [
 {
  "LEID": "123",
  "result": [
    {
      "CCID": "456",
      "result": [
        {
          "Amount": 10000,
          "NNID": "789"
        }
      ]
    },
    {
      "CCID": "ABC",
      "result": [
        {
          "Amount": 5000,
          "NNID": "DEF"
        }
      ]
    }
  ]
}
]
}

What i'm trying to do is get the following out:

{"LEID":123,"CCID":456,"NNID":789}

{"LEID":123,"CCID":ABC,"NNID":DEF}

So get a trio of LEID, CCID and NNID

So far what I have is:

  LEID_collection = response['result']
  LEID = LEID_collection.map {|h| h['LEID']}
  LEID = LEID.reduce
  CCID_collection = LEID_collection.reduce
  CCIDs = CCID_collection['result'].map {|h|h['CCID']}
  CCID1 = CCIDs[0]
  CCID2 = CCIDs[1]
  CCIDs = CCID_collection['result']
  test = CCIDs.first.keys.zip(CCIDs.map(&:values).transpose).to_h
  test2 = test['result']
  test3 = test2.flatten
  test4 = test3.map {|h| h['NNID']}
  NNID1 = test4[0]
  NNID2 = test4[1]

  hash1 = Hash["LEID", LEID, "CCID", CCID1, "NNID", NNID1]
  puts "hash 1 :" +  hash1.to_s
  hash2 = Hash["LEID", LEID, "CCID", CCID2, "NNID", NNID2]
  puts "hash 2 :" +  hash2.to_s

This gets what I want but is really not dynamic... are there any better ways?

Sorry for how convoluted this is, i'm just not sure how to explain it any other way. Happy to answer any questions.

Sorry you're right I need to edit my comment to use {} to show i want hashes not arrays - thank you for pointing that out. Sorry i'm new to all this. — A Cox
– A Cox, Commented Feb 6, 2018 at 10:55

Paul Martensen · Accepted Answer · 2018-02-06 11:48:13Z

1

If you know that you'll always have this structure and you use ruby >= 2.3.0, then you can use the dig method to shorten things:

collection = response['result'].first
trios = collection['result'].map do |ccid|
  {
    'LEID' => collection['LEID'],
    'CCID' => ccid['CCID'],
    'NNID' => ccid.dig('CCID', 'NNID')
  }
end

Its only a little shorter but hopefully easier to read overall.

answered Feb 6, 2018 at 11:48

Paul Martensen

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3 Comments

A Cox Over a year ago

Thank you i'll take a look at it - unfortunately this is just the first step, as I know later on i'll have more NNID's under the CCIDs....and will have to form trios of those...but this could be a good place to start!

SRack Over a year ago

In case it's needed here, prior to 2.3 you could chain .try(:[], :key) as a substitute for :dig. Not pretty, but works to the same goal.

Paul Martensen Over a year ago

try only works in rails though mind you.

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