nl2br, strtr php functions in ruby

For those who are php code know very well how important is strtr and nl2br in the web development.

When developing web application in rails I still need these 2 functions. so I dicide just to keep and implement the same name in ruby:
string.rb

class String
  def str_translate values, preserve = false
     self.gsub /\{[^\}]*\}/ do |match|
           key = match[1..-2]
            if preserve
              values[key.to_sym] || match
           else
              values[key.to_sym] || ""
           end
     end
  end

 def nl2br
    self.gsub /\n/ do |match|
          <br />
    end
  end
end

string_spec.rb

require "spec_helper"

describe String do
  describe "#str_translate" do
      it "should be translated keys in the string by parameters in the list " do
        str = "The message from {user} sent out on {day} "
        strtr = str.str_translate(:user => "Ilab", :day => "Monday")
        strtr.should eq "The message from Ilab sent out on Monday "
      end

      it "should preserve keys that not in the string by parameters in the list " do
        str = "The message from {user} sent out on {day} "
        strtr = str.str_translate({:day => "Monday"}, true)
        strtr.should eq "The message from {user} sent out on Monday "
      end

      it "should remove the missing key from the string" do
        str = "The message from {user} sent out on {day} "
        strtr = str.str_translate(:day => "Monday")
        strtr.should eq "The message from  sent out on Monday "
      end
  end

  describe "nl2br -new line to br" do
    it "should convert all new line to br" do
      original = ["\nthis is a great new\nIn the \n", "blah\n\n\nblah\n"]
      converted = ["<br />this is a great new<br />In the <br />", "blah<br /><br /><br />blah"]
      original.each_with_index do |str, index|
        str.nl2br.should eq converted[index]
      end
    end
  end
end