hash.rb

class Hash
  # merge_present
  # examples:
  #    {hello: ''}.merge_present(hello: 'sd') #=> {hello: 'sd'}
  #
  #    {hello: nil}.merge_present(hello: '') #=> {}
  #
  def merge_present(other_hash)
    mapped = self.map do |k, v|
      if v.blank?
        if _new = other_hash[k.to_s].presence
          [k, _new]
        else
          [k, nil]
        end
      else
        [k, v]
      end
    end
    Hash[mapped].compact
  end
end