Getting an array of hash values given specific keys

Question

Given certain keys, I want to get an array of values from a hash (in the order I gave the keys). I had done this:

class Hash

  def values_for_keys(*keys_requested)
    result = []
    keys_requested.each do |key|
      result << self[key]
    end
    return result
  end

end

I modified the Hash class because I do plan to use it almost everywhere in my code.

But I don't really like the idea of modifying a core class. Is there a builtin solution instead? (couldn't find any, so I had to write this).

you could also write a utility class where ur function will take hash and keys as params. — Learn More
– Learn More, Commented Aug 5, 2013 at 4:55

mu is too short · Accepted Answer · 2019-03-14 17:21:41Z

5

You should be able to use values_at:

values_at(key, ...) → array

Return an array containing the values associated with the given keys. Also see Hash.select.
h = { "cat" => "feline", "dog" => "canine", "cow" => "bovine" }
h.values_at("cow", "cat")  #=> ["bovine", "feline"]

The documentation doesn't specifically say anything about the order of the returned array but:

The example implies that the array will match the key order.
The standard implementation does things in the right order.
There's no other sensible way for the method to behave.

For example:

>> h = { :a => 'a', :b => 'b', :c => 'c' }
=> {:a=>"a", :b=>"b", :c=>"c"}
>> h.values_at(:c, :a)
=> ["c", "a"]

edited Mar 14, 2019 at 17:21

answered Aug 5, 2013 at 5:09

mu is too short

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Comments

Sahil Dhankhar · Accepted Answer · 2013-08-05 04:54:18Z

0

i will suggest you do this:

your_hash.select{|key,value| given_keys.include?(key)}.values

answered Aug 5, 2013 at 4:54

Sahil Dhankhar

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