Hash Merge

hash.rb

# Remove duplicate keys
array = [ Hash[ burger: 1], Hash[burger: 2, pie: 1] ]
array.reduce({}) do |result, department| 
  result.merge(department) do |key, left, right| 
    left + right 
  end
end
# {:burger=>3, :pie=>1}

# Override the right hash with the left
default_vehicles = Hash[ car: "red" ]
vehicles         = Hash[ car: "blue", bike: "green", truck: "yellow" ]
vehicles_colours = default_vehicles.reverse_merge(vehicles)
# {:car=>"red", :bike=>"green", :truck=>"yellow"}