Convert string into Currency format

Question

Using Ruby and Haml, I have a property which is cost. I believe (im new to ruby) that it will be a Float

At the moment the below line outputs my decimal in format like 4.5 instead of 4.50, which is what I want.

%span.value= "£#{event.beers.first.cost)}"

This is my class file for beers.

class Beer
  include Mongoid::Document
  embeds_many :ratings

  field :name, type: String
  field :country, type: Country
  field :cost, type: Float
  field :photos, type: PhotoArray, default: PhotoArray.new
end

Answer 1

In case you're using Rails you can use number_to_currency helper

Answer 2

If you're talking about American currency including:

• commas every three digits left of the decimal point
• at most two digits right of the decimal point
• don't show decimal point if there are zero cents

try this

vals = [123.01, 1234.006, 12, 1234567, 12345678.1,1.001]
vals.map{|num| 
            num.sprintf('%.2f',num)
               .gsub('.00','')
               .reverse
               .scan(/(\d*\.\d{1,3}|\d{1,3})/)
               .join(',')
               .reverse
        }

Which generates the following in a debugger:

=> ["123.01", "1,234.01", "12", "1,234,567", "12,345,678.10", "1"]

It can be tweaked to be useful for some of the European formats by editing the join string, but I don't know much about the European conventions.