Is there a clean way to access hash values in array of hashes?

Question

In this code:

arr = [ { id: 1, body: 'foo'}, { id: 2, body: 'bar' }, { id: 3, body: 'foobar' }]
arr.map { |h| h[:id] } # => [1, 2, 3]

Is there a cleaner way to get the values out of an array of hashes like this?

Underscore.js has pluck , I'm wondering if there is a Ruby equivalent.

Answer 1

If you don't mind monkey-patching, you can go pluck yourself:

arr = [{ id: 1, body: 'foo'}, { id: 2, body: 'bar' }, { id: 3, body: 'foobar' }]

class Array
  def pluck(key)
    map { |h| h[key] }
  end
end

arr.pluck(:id)
=> [1, 2, 3]
arr.pluck(:body)
=> ["foo", "bar", "foobar"]

Furthermore, it looks like someone has already generalised this for Enumerables , and someone else for a more general solution .

Answer 2

Now rails support Array.pluck out of the box. It has been implemented by this PR

It is implemented as:

def pluck(key)
  map { |element| element[key] }
end

So there is no need to define it anymore :)

Answer 3

Unpopular opinion maybe, but I wouldn't recommend using pluck on Array in Rails projects since it is also implemented by ActiveRecord and it behaves quite differently in the ORM context (it changes the select statement):

User.all.pluck(:name) # Changes select statement to only load names
User.all.to_a.pluck(:name) # Loads the whole objects, converts to array, then filters the name out

Therefore, to avoid confusion, I'd recommend using the shorten map(&:attr) syntax on arrays :

arr.map(&:name)