A Ruby mixin library to add simple money display and editing using data stored as an integer in cents or other precision or currency. Easy Money is a simpler alternative to the “money” gem, and easier to use, hence the name.
Float types are not good for storing and computing financial data because of rounding and conversion between floats and decimal precision and slower performance compared to integer arithmetic. Integers are preferred in this case, with a dollar amount ($1.00) stored as cents (100) internally.
Easy Money will also handle any float data stored as integer in the database for this reason, such as FM Radio Frequencies (88.1 FM) or an NTRP Tennis Rating (4.5).
Easy Money works in any Ruby class, it does not require Active Record or other ORM. Its default setting allow it to work on US Dollar amounts stored in cents, but is easily configured.
First, install this from gemcutter
gem install easy_money
Next, you need to configure your app to use it, by either:
require 'rubygems' # Rails application, no framework require 'easy_money' # config.gem 'easy_money' # Rails 2.x, in your ./config/environment.rb gem 'easy_money' # Rails 3.x, in your ./Gemfile
Mixin the EasyMoney module into the (model) class you need, and declare the attributes (columns) you wish you have the easy_money helpers
class Ledger include EasyMoney attr_accessor :amount, :euro # Integer value of cents easy_money :amount # Creates amount_money() and amount_money=() methods easy_money :amount, :units=>"dollars", :unit=>'$', :negative=>'%.2f CR' # Creates amount_dollars() and amount_dollars=() methods end ledger = Ledger.new ledger.amount = 100 # 100 cents = $1.00 ledger.amount_money #=> "1.00" ledger.amount_money = "-123.45" ledger.amount #=> -12345 (cents) ledger.amount_money(:negative=>'%.2f CR', :zero=>'Free') # Uses these formats ledger.amount_dollars #=> "$123.45 CR" # Track the bets of the Gamesters of Triskelion on their drill thrall competitions. class ProviderWagers < ActiveRecord::Base include EasyMoney easy_money :quatloos, :units=>'quatloos', :precision=>3, :zero=>'even', :nil=>'no bet', :negative=>'%.3f Loss', :unit=>'Q', :negative_regex=>/^(-?)(.+\d)\s*Loss/i # creates amount_quatloos(), amount_quatloos=() end # in your views <%= f.text_field :amount_quatloos %> # -12000 => "Q12.000 Loss"
Options for Easy Money calls:
:money_method - Use this as the alternative name to the money-access methods
:units - Use this as an alternative suffix name to the money methods ('dollars' gives 'xx_dollars')
:precision - The number of digits implied after the decimal, default is 2
:separator - The character to use after the integer part, default is '.'
:delimiter - The character to use between every 3 digits of the integer part, default none
:positive - The sprintf format to use for positive numbers, default is based on precision
:negative - The sprintf format to use for negative numbers, default is same as :positive
:zero - The sprintf format to use for zero, default is same as :positive
:nil - The sprintf format to use for nil values, default none
:unit - Prepend this to the front of the money value, say '$', default none
:blank - Return this value when the money string is empty or has no digits on assignment
:negative_regex - A Regular Expression used to determine if a number is negative (and without a - sign), defaults to having a “CR” after the number
Easy Money Formatters
You can also call or build your own custom conversions. Ensure that you can convert between the integer and money forms if you need to.
The “money” type is a string, sutitable for human editing, and will convert back into integer type. If you override the formatting options, test that your money result string will convert properly back to the original integer value.
include EasyMoney ... puts EasyMoney.money_to_integer( money_string, :option=>value, ... ) puts EasyMoney.integer_to_money( cents_integer, :option=>value, ... ) puts EasyMoney.integer_to_float( cents_integer, :option=>value, ... ) puts EasyMoney.float_to_integer( money_float, :option=>value, ... ) EasyMoney.integer_to_float( nil, blank:0.0 ) #=> 0.0 [Ruby 1.9.1 Syntax] EasyMoney.integer_to_float( 12345, :precision=>3 ) #=> 12.345 EasyMoney.float_to_integer(12.345111, :precision=>3 ) #=> 12345
The options to these methods are the same as the #easy_money declarations
Validate Money string format
Global configuration for currency settings
Explore rounding vs. truncation issues
Use a Locale and I18n on money formatting, without introducing dependencies (perhaps by injection)?
Explore inegration of Rails' NumberHelper methods, but not require ActionView
Custom converters (useful for say, converting bytes to Gigabytes)?
Copyright © 2010 Allen Fair. See LICENSE for details.