convert string to integer

[jitao]

Hi I have a question and need your help.

How can I convert a string like "6.09B" to an integer 6,090,000,000 or "34.2M" to 34,200,000 ?

which method should I use can you give me a example?

Thank you!

[ReggieB]

There are a number of ways you could do it, but the simplest is probably to create a new class to handle the conversion. For example, you could create a StringTo class and use that to handle various conversions. For your current problem you'd use a class method of 'integer', so it would look something like this:

number = StingTo.integer("6.09B")

So to do this, you'd first write a unit test class. This is what I ended up with:

$:.unshift File.join(File.dirname(__FILE__),'..','lib')

require 'test/unit'
require 'string_to'

class TestStringTo < Test::Unit::TestCase
  def setup
    @decimal_text = "1.1"
    @integer_text = "100"
    @fraction_text = ".45"
    @invalid_text = "X"
    @invalid_postscript = "1.1X"
    @valid_test_strings = [@decimal_text, @integer_text, @fraction_text]
  end
  
  def test_millions
    for test_string in @valid_test_strings
      @string = "#{test_string}M"
      @target = (test_string.to_f * (10**6)).to_i
      assert_output_matches_target
    end
  end

  def test_billions
    for test_string in @valid_test_strings
      @string = "#{test_string}B"
      @target = (test_string.to_f * (10**9)).to_i
      assert_output_matches_target
    end
  end

  def test_decimal
    for test_string in @valid_test_strings
      @string = "#{test_string}"
      @target = test_string.to_i
      assert_output_matches_target
    end
  end

  def test_invalid
    assert_raise RuntimeError do
      StringTo.integer(@invalid_text)
    end
    assert_raise NoMethodError do
      StringTo.integer(@invalid_postscript)
    end
  end

  private
  def assert_output_matches_target
    assert_equal @target, StringTo.integer(@string)
  end
end

As you write the test you can start writing the class. This is what I ended up with:

class StringTo
  CONVERSIONS = {'M' => 6, 'B' => 9}

  def self.integer(string)
    number_followed_by_single_letter_pattern = /^(\d+|\d+\.\d*|\d*\.\d+)(\D)$/
    number_only_pattern = /^(\d+|\d+\.\d*|\d*\.\d+)$/
    if string =~ number_followed_by_single_letter_pattern
      return ($1.to_f * (10 ** CONVERSIONS[$2])).to_i
    elsif string =~ number_only_pattern
      return string.to_i
    else
      raise
    end
  end
end

[jitao]

Thankyou, this is awesome. I'll follow your every post, my lord.