Access Ruby Hash Using Dotted Path Key String

Question

The Rails I18n library transforms a YAML file into a data structure that is accessible via a dotted path call using the t() function.

t(\'one.two.three.four\         


        

Answer 1

This code not only allows dot notation to traverse a Hash but also square brackets to traverse Arrays with indices. It also avoids recursion for efficiency.

class Hash

  def key_path(dotted_path)
    result = self
    dotted_path.split('.').each do |dot_part|
      dot_part.split('[').each do |part|
        if part.include?(']')
          index = part.to_i
          result = result[index] rescue nil
        else
          result = result[part] rescue nil
        end
      end
    end

    result
  end

end

Example:

a = {"b" => {"c" => [0, [1, 42]]}}
a.key_path("b.c[-1][1]") # => 42