Create new array with key from an existing array - Ruby

Question

I have this hash:

my_hash = [
  {
    :name=> 'fiat 500',
    :things=> %w[gps bluetooth automatico],
    :year=> '2021'
  },
  {
    :name=> 'fusca',
    :things=> %w[som dvd automatico],
    :year=> '2022'
  }

]

I want to create a new array but only with the key :year, where would be like this:

 new_array = [
 {
    :year=> '2021'
  },
  {
    :year=> '2022'
  }
]

I'm a beginner in ruby and I can't do it.

"I have this hash: my_hash = [...]" – that's actually an array. — Stefan
– Stefan, Commented Jan 21, 2022 at 9:15

Yakov · Accepted Answer · 2022-01-21 09:27:16Z

3

I'd use map and slice methods:

new_array = my_array.map { |item| item.slice(:year) }

answered Jan 21, 2022 at 9:27

Yakov

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4 Comments

Jad Over a year ago

just for note, between the 2 answers. in the case that there is no "year" in a record of the array, this one returns an empty hash, and the other answer returns a hash with the :year set to nil

Yakov Over a year ago

That's true. As it's not stated in the question I assume that the key is always present.

Bhushan Kalode Over a year ago

Instead of my_array, it should be my_hash - @Yakov

Yakov Over a year ago

@BhushanKalode it's my_hash in the question, but actually, it's an array of hashes

Yakov · Accepted Answer · 2022-02-10 08:12:37Z

1

You can use the method map for that.

Ruby doc: https://ruby-doc.org/core-3.0.0/Array.html#method-i-map

new_array = my_hash.map { |h| { :year => h[:year] } }

edited Feb 10, 2022 at 8:12

Yakov

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answered Jan 21, 2022 at 8:50

BTL

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1 Comment

Yakov Over a year ago

sorry, I accidentally edited your answer instead of mine. I've reverted it back.

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