Duplicating a Ruby array of strings

Your second solution can be shortened to arr2 = arr.map do |e| e.dup end (unless you actually need the behaviour of clone, it's recommended to use dup instead).

Other than that your two solutions are basically the standard solutions to perform a deep copy (though the second version is only one-level deep (i.e. if you use it on an array of arrays of strings, you can still mutate the strings)). There isn't really a nicer way.

Edit: Here's a recursive deep_dup method that works with arbitrarily nested arrays:

class Array  def deep_dup    map {|x| x.deep_dup}  endendclass Object  def deep_dup    dup  endendclass Numeric  # We need this because number.dup throws an exception  # We also need the same definition for Symbol, TrueClass and FalseClass  def deep_dup    self  endend

You might also want to define deep_dup for other containers (like Hash), otherwise you'll still get a shallow copy for those.

I recommend your initial idea, but written slightly more concisely:

arr = ["red","green","yellow"]arr2 = arr.inject([]) { |a,element| a << element.dup }

I am in a similar situation and very concerned about speed. The fastest way for me was to make use of map{&:clone}

So try this:

pry(main)> a = (10000..1000000).to_a.shuffle.map(&:to_s)pry(main)> Benchmark.ms { b = a.deep_dup }                                                                                     => 660.7760030310601pry(main)> Benchmark.ms { b = a.join("--!--").split("--!--") }=> 605.0828141160309pry(main)> Benchmark.ms { b = a.map(&:clone) }=> 450.8283680770546