Ruby create an array of hashes

Question

I've got a variable I'd like to use as a key to a hash that contains its own key and array.

e.g.

custArray = Array.new
custArray << {"c1001" => {"purchases" => ["prod01"]}}

I want to be able to do something like:

if custArray[:c1001].exists?
  custArray[{:c1001["purchases"]} << "prod02"]
end

but I'm just totally stuck.

Prefer cust_array over custArray in Ruby. Also, "c1001" and :c1001 are not equivalent hash keys. — yzalavin
– yzalavin, Commented May 7, 2018 at 15:11
I suggest that in future you not be in such a rush to select an answer. There's no hurry. — Cary Swoveland
– Cary Swoveland, Commented May 7, 2018 at 18:02

Fran Martinez · Accepted Answer · 2018-05-07 16:30:06Z

3

You can resolve it with:

if c = custArray.find { |h| h.key? 'c1001' }
  c.dig('c1001', 'purchases') << "prod2"
end

Or if you can have more than one result with this key:

custArray.select { |h| h.key? 'c1001' }.each do |c|
  c.dig('c1001', 'purchases') << "prod2"
end

answered May 7, 2018 at 16:30

Fran Martinez

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Comments

3limin4t0r · Accepted Answer · 2018-05-07 16:06:15Z

2

If you only want to update the first instance of the array you can do:

target = custArray.find { |hash| hash.key? 'c1001' }
target['c1001']['purchases'] << 'prod02' if target

If you want to update all instances of the array you can do (backslashes are for console purposes only):

custArray \
  .select { |hash| hash.key? 'c1001' } \
  .each { |hash| hash['c1001']['purchases'] << 'prod02' }

answered May 7, 2018 at 16:06

3limin4t0r

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Comments

lacostenycoder · Accepted Answer · 2018-05-08 00:32:01Z

2

You can use select from the array of hashes to see if the key is there:

target = custArray.find { |h| h.key? 'c1001' }
target['c1001']['purchases'] <<  "prod02" unless target.nil?

Or if array contains multiple hashes with the same key:

custArray.select { |h| h.key? 'c1001' }.each do |h|
  h['c1001']['purchases'] <<  "prod02" 
end

edited May 8, 2018 at 0:32

answered May 7, 2018 at 15:08

lacostenycoder

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3 Comments

Toph Over a year ago

Apologies, I edited the question. That absolutely worked.

lacostenycoder Over a year ago

I edited my answer as the first answer I gave was incorrect

lacostenycoder Over a year ago

See last update. But also be aware, an array may contain multiple hashes that have the same keys. So make sure however you're building your array, those keys are unique. Also prefer snake case in ruby cust_array vs custArray.

Leo · Accepted Answer · 2018-05-07 15:30:33Z

1

Also, you can write something similar to code that you already provide

custArray.each do |h|
  h['c1001']['purchases'] << 'prod02' if h.keys.include?('c1001')
end

That allows reducing the count of iteration loops

answered May 7, 2018 at 15:30

Leo

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1 Comment

lacostenycoder Over a year ago

This solution will also handle if you have duplicate array values with the same hash key c1001

Cary Swoveland · Accepted Answer · 2018-08-07 19:42:24Z

0

custArray.find { |h| h.key?('c1001') }&.dig('c1001', 'purchases')&.push("prod02")
  #=> ["prod01", "prod02"]
custArray
  #=> [{"c1001"=>{"purchases"=>["prod01", "prod02"]}}]

custArray.find { |h| h.key?('c1002') }&.dig('c1002', 'purchases')&.push("prod02")
  #=> nil
custArray
  #=> [{"c1001"=>{"purchases"=>["prod01"]}}]

custArray.find { |h| h.key?('c1001') }&.dig('c1001', 'popsicles')&.push("prod02")
  #=> nil
custArray
  #=> [{"c1001"=>{"purchases"=>["prod01"]}}]

& is Ruby's Safe Navigation Operator. See also Hash#dig. Both made their debut in Ruby v2.3.

answered Aug 7, 2018 at 19:42

Cary Swoveland

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