ruby - Unique on an array of hashes based on value

Question

I feel like this could be improved (a common feeling in ruby). I'm trying to uniq an array of hashes based on value. In this example, I want the colors of the elements. Moss and snow are impostors.

# remove unique array of hashes based on a hash value

a = [
  { :color => "blue", :name => "water" },
  { :color => "red", :name => "fire" },
  { :color => "white", :name => "wind" },
  { :color => "green", :name => "earth" },
  { :color => "green", :name => "moss" },
  { :color => "white", :name => "snow" }
]

# remove moss and snow
uniques = []
a.each_with_index do |r, i|
  colors = uniques.collect {|e| e[:color]}

  if !colors.include? r[:color]
    uniques.push r
  else
    a[i] = nil
  end
end

a.compact!

puts a

This will print

{:color=>"blue", :name=>"water"}
{:color=>"red", :name=>"fire"}
{:color=>"white", :name=>"wind"}
{:color=>"green", :name=>"earth"}

Which is "correct" however I feel like this is excessive. My experience with .map .inject is limited and those advanced techniques elude me. If someone could re-factor this, it might help me understand another terse technique.

question from:https://stackoverflow.com/questions/4841187/unique-on-an-array-of-hashes-based-on-value

Answer 1

In Ruby 1.9, try the following

a.uniq! {|e| e[:color] }