Rails: Is there a rails trick to adding commas to large numbers?

Question

Is there a way to have rails print out a number with commas in it?

For example, if I have a number 54000000.34, I can run <%= number.function %>, which would prin

Answer 1

If you're doing it a lot but also FYI because it's not implied by the above, Rails has sensible defaults for the number_with_delimiter method.

#inside controller or view
number_with_delimiter(2444323.4)
#=> 2,444,323.30

#inside console
helper.number_with_delimiter(233423)
#=> 233,423

No need to supply the delimiter value if you're doing it the most typical way.

Answer 2

Yes, use the NumberHelper. The method you are looking for is number_with_delimiter.

 number_with_delimiter(98765432.98, :delimiter => ",", :separator => ".")
 # => 98,765,432.98

Answer 3

A better way for those not using rails that handles decimals:

parts = number.to_s.split('.')
parts[0].gsub!(/(\d)(?=(\d\d\d)+(?!\d))/, "\\1,")
parts.join('.')

If you want a different delimiter, change the last ',' in the regex.

For bonus, this is how the regex is working:

• gsub replaces everything that matches the regex with the second parameter passed to gsub. In this case that is \\1. \\1 becomes \1 when evaluated which matches the first capture group in the regex. In this regex that is (\d).
• (\d)(?=(\d\d\d)+) is matching a digit followed by 1 or more groups of 3 digits. The first set of parens is our \1 capture group, the second would be \2. If we were just to leave it at that we would get: 123456.gsub!(/(\d)(?=(\d\d\d)+)/, "\\1,") #=> 1,2,3,456 This is because 1234 matches, 2345 matches and 3456 matches so we put a comma after the 1, the 2, and the 3.
• By adding the (?!\d) we are matching anything that comes before that doesn't precede a digit so (\d)(?=(\d\d\d)+(?!\d)) means match a digit followed by 3 digits that is not followed by a digit. The reason why this works is that gsub will keep replacing things that match the string. If we were only going to replace the first match then for a number like 123456789 we would get 123456,789. Since 123456,789 still matches our regex we get 123,456,789.

Here is where I got the code: https://github.com/rails/rails/blob/master/activesupport/lib/active_support/number_helper.rb#L298-L300

And here is where I learned about what is going on in that regex: http://www.tutorialspoint.com/ruby/ruby_regular_expressions.htm

Answer 4

The direct way to do this, with or without Rails, is:

require 'active_support/core_ext/numeric/conversions'

12345.to_s(:delimited)      # => "12,345"
12345.6789.to_s(:delimited) # => "12,345.6789"

For more options, see Active Support Core Extensions - Numeric - Formatting.

Answer 5

The following do the trick for both delimiter and precision (API ref).

ActiveSupport::NumberHelper.number_to_rounded(1234.532, delimiter: ',', precision: 1) 

(or from views just number_to_rounded, no need for the suffix)

HTH

Answer 6

You want the number_with_delimiter method. For example:

<%= number_with_delimiter(@number, :delimiter => ',') %>

Alternatively, you can use the number_with_precision method to ensure that the number is always displayed with two decimal places of precision:

<%= number_with_precision(@number, :precision => 2, :delimiter => ',') %>