hash containing an array to array of hashes in ruby

Question

I've read through quite a few of posts, but none seem to do just this, which is a bit tricky.

Say I have a hash that contains an array as one of its values.

hash = {
  :a => 'one', 
  :arr => [
    {:id => 'ten',    :amount => 10, :b => 'two'}, 
    {:id => 'twenty', :amount => 20, :b => 'two'},
    {:id => 'apple',  :amount => 7,  :b => 'applesauce'}
  ], 
  :c => 3
}

I want to convert this to an array of hashes (which would be of the size of the contained array), as follows:

# => [
  {:a => 'one', :id => 'ten',    :amount => 10, :b => 'two',        :c => 3},
  {:a => 'one', :id => 'twenty', :amount => 20, :b => 'two',        :c => 3},
  {:a => 'one', :id => 'apple',  :amount => 7,  :b => 'applesauce', :c => 3}
]

The conversion should maintain whatever key/value pairs are inside and outside the array, and ideally I could pass in the key of the array to ask it perform the action:

flatten_hash_array(hash, :arr)

I realize that the Ruby flatten in the Array class is not what we need. Grasping for a verb! Any help would be appreciated.

Chowlett · Accepted Answer · 2012-02-03 17:31:44Z

5

This should do the job, barring validity checks.

def flatten_hash_array(hash, key)
  hash[key].map {|entry| entry.merge(hash.reject {|k| k == key})}
end

answered Feb 3, 2012 at 17:31

Chowlett

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2 Comments

adamrneary Over a year ago

Awesome! the hash.reject block just needs to be passed k,v and it works like a charm. Thanks! def flatten_hash_array(hash, key) hash[key].map {|entry| entry.merge(hash.reject {|k,v| k == key})} end

Chowlett Over a year ago

Hmm, must be a 1.8 / 1.9 difference - my Ruby accepts hash.reject {|k|}, even though there are two params available. But hey - glad it works for you.

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