Question

I have an application that handles currency inputs. However, if you’re in the US, you might enter a number as 12,345.67; in France, it might be 12.345,67.

Is there an easy way, in Rails, to adapt the currency entry to a locale?

Note that I’m not looking for display of the currency (ala number_to_currency), I’m looking to deal with someone typing in a currency string, and converting it into a decimal.

Answer 1

You could give this a shot:

   def string_to_float(string)

      string.gsub!(/[^\d.,]/,'')          # Replace all Currency Symbols, Letters and -- from the string

      if string =~ /^.*[\.,]\d{1}$/       # If string ends in a single digit (e.g. ,2)
        string = string + "0"             # make it ,20 in order for the result to be in "cents"
      end

      unless string =~ /^.*[\.,]\d{2}$/   # If does not end in ,00 / .00 then
        string = string + "00"            # add trailing 00 to turn it into cents
      end

      string.gsub!(/[\.,]/,'')            # Replace all (.) and (,) so the string result becomes in "cents"  
      string.to_f / 100                   # Let to_float do the rest
   end

And the test Cases:

describe Currency do
  it "should mix and match" do
    Currency.string_to_float("$ 1,000.50").should eql(1000.50)
    Currency.string_to_float("€ 1.000,50").should eql(1000.50)
    Currency.string_to_float("€ 1.000,--").should eql(1000.to_f)
    Currency.string_to_float("$ 1,000.--").should eql(1000.to_f)    
  end     

  it "should strip the € sign" do
    Currency.string_to_float("€1").should eql(1.to_f)
  end

  it "should strip the $ sign" do
    Currency.string_to_float("$1").should eql(1.to_f)
  end

  it "should strip letter characters" do
    Currency.string_to_float("a123bc2").should eql(1232.to_f)
  end

  it "should strip - and --" do
    Currency.string_to_float("100,-").should eql(100.to_f)
    Currency.string_to_float("100,--").should eql(100.to_f)
  end

  it "should convert the , as delimitor to a ." do
    Currency.string_to_float("100,10").should eql(100.10)
  end

  it "should convert ignore , and . as separators" do
    Currency.string_to_float("1.000,10").should eql(1000.10)
    Currency.string_to_float("1,000.10").should eql(1000.10)
  end

  it "should be generous if you make a type in the last '0' digit" do
    Currency.string_to_float("123,2").should eql(123.2)
  end