flat_map (Enumerable)

@avibryant @chadfowler is this what you are talking about?

Returns a new array with the concatenated results of running block once for every element in enum . If no block is given, an enumerator is returned instead. [[ 1 , 2 ],[ 3 , 4 ]]. flat_map {| i | i } #=> [1, 2, 3, 4]

Full article: http://apidock.com/ruby/Enumerable/flat_map