ruby - Create own Array#map like method

Question

I want to create an instance method like Array#my_map and that method should behavior of the original Array#map method. I want to same output from new method as below:

arr = [1, 2, 3, 4]
arr.new_map_method do |x|
 x + 1
end # => [2, 3, 4, 5]

arr.new_map_method(&:to_s) # => ["1", "2", "3", "4"]

Answer 1

The easiest way of creating a method with the same behavior of a different method is a simple alias:

class Array
  alias_method :new_map_method, :map
end

If, for whatever strange reason, you don't want to use map, you can use inject instead:

class Array
  def new_map_method
    return enum_for(__callee__) unless block_given?
    inject([]) {|acc, el| acc << yield(el) }
  end
end