class Xchange

An instance of Xchange represents an amount of a specific currency.

Usage¶ ↑

Install¶ ↑

gem install Xchange

Require `Xchange`¶ ↑

require 'xchange'

Configure the currency rates with respect to a base currency¶ ↑

Xchange.conversion_rates('EUR', {'USD' => 1.11, 'Bitcoin' => 0.0047})

Instantiate `Xchange` objects¶ ↑

fifty_eur = Xchange.new(50, 'EUR')

Get amount and currency¶ ↑

fifty_eur.amount   # => 50

fifty_eur.currency # => "EUR"

fifty_eur.inspect  # => "50.00 EUR"

Convert to a different currency¶ ↑

fifty_eur.convert_to('USD') # => 55.50 USD

Perform operations in different currencies¶ ↑

twenty_dollars = Xchange.new(20, 'USD')

# Arithmetics:

fifty_eur + twenty_dollars # => 68.02 EUR

fifty_eur - twenty_dollars # => 31.98 EUR

fifty_eur / 2              # => 25 EUR

twenty_dollars * 3         # => 60 USD

# Comparisons (also in different currencies):

twenty_dollars == Xchange.new(20, 'USD') # => true

twenty_dollars == Xchange.new(30, 'USD') # => false

fifty_eur_in_usd = fifty_eur.convert_to('USD')

fifty_eur_in_usd == fifty_eur          # => true

twenty_dollars > Xchange.new(5, 'USD')   # => true

twenty_dollars < fifty_eur             # => true

Constants

VERSION

Attributes

amount_bigdecimal[R]

Accessor method

currency[R]

Accessor method

Public Class Methods

conversion_rates(base_currency, rates) click to toggle source

Class method that configure the currency rates with respect to a base currency

@example
  Xchange.conversion_rates('EUR',{'USD' => 1.11, 'bitcoin' => 0.00047})

# File lib/xchange.rb, line 94
def self.conversion_rates(base_currency, rates)

  @@base_currency = base_currency

  @@rates = rates

end

new(amount, currency) click to toggle source

Creates a new Xchange object of value given by amount parameter, with the currency given by the currency parameter

@example
  Xchange.new(100, "USD") #=> "100.00 USD"
  Xchange.new(100, "EUR") #=> "100.00 EUR"

# File lib/xchange.rb, line 81
def initialize (amount, currency)

  #Amount is stored in BigDecimal for better precision in currency operations
  @amount_bigdecimal = BigDecimal.new(amount,0)

  @currency = currency

end

Public Instance Methods

*(number) click to toggle source

Multiplies the amount by a given number

# File lib/xchange.rb, line 188
def *(number)

  #performs the multiplication in BigDecimal
  amount= @amount_bigdecimal * BigDecimal(number,0)

  #returns the result as a new instance
  Xchange.new(amount,@currency)

end

+(another_currency) click to toggle source

Performs an addition between the current instance and another one and returns the result as a new Xchange instance

# File lib/xchange.rb, line 165
def +(another_currency)

  #converts the given instance in the actual currency and sums the amounts
  amount = @amount_bigdecimal + another_currency.convert_to(@currency).amount

  #returns the result as a new instance
  Xchange.new(amount,@currency)

end

-(another_currency) click to toggle source

Performs a subtraction between the current instance and another one and returns the result as a new Xchange instance

# File lib/xchange.rb, line 177
def -(another_currency)

  #converts the given instance in the actual currency and substracts the amounts
  amount= @amount_bigdecimal - another_currency.convert_to(@currency).amount

  #returns the result as a new instance
  Xchange.new(amount,@currency)

end

/(number) click to toggle source

Divides the amount by a given number

# File lib/xchange.rb, line 199
def /(number)

  #performs the division in BigDecimal
  amount= @amount_bigdecimal / BigDecimal(number,0)

  #returns the result as a new instance
  Xchange.new(amount,@currency)

end

<=>(another_currency) click to toggle source

<=> implementation allows the comparison between two Xchange instances through the Comparable mixin

# File lib/xchange.rb, line 156
def <=>(another_currency)

  #converts the given instance in the actual currency and compares the amounts
  @amount_bigdecimal <=> another_currency.convert_to(@currency).amount_bigdecimal

end

amount() click to toggle source

Convenience method for amount, it returns the value in float rounded by two decimals.

# File lib/xchange.rb, line 103
def amount

  @amount_bigdecimal.to_f.round(2)

end

convert_to(new_currency) click to toggle source

Converts an instance to another currency

@example
Xchange.new(50, 'EUR').convert_to('USD') #=> "55.50 USD"

# File lib/xchange.rb, line 120
def convert_to(new_currency)

  # if the instance is already in the requested currency
  if @currency == new_currency

    #returns itself without conversions
    return self

  # if  the current currency is different from the base currency used for conversions
  # and also the new currency is different from the base one
  elsif @currency != @@base_currency && new_currency != @@base_currency

    # amount is divided by the rate of the current currency in order to convert it to the base currency
    # then is multiplied by the rate of the new currency
    amount = (@amount_bigdecimal/(BigDecimal(@@rates[@currency],0))) * (BigDecimal(@@rates[new_currency],0))

  # current currency is different from the base currency but new currency equals the base currency
  elsif @currency != @@base_currency && new_currency == @@base_currency

    # amount is divided by the rate of the current currency in order to convert it to the base currency
    amount = (@amount_bigdecimal  / @@rates[@currency])

  # current currency must be equal to the base currency and be different from the new currency
  else

    # amount is multiplied for the rate of the new currency
    amount = @amount_bigdecimal * (BigDecimal.new(@@rates[new_currency],0))

  end

  # A new istance is returned with the new currency and the calculated amount
  Xchange.new(amount,new_currency)

end

inspect() click to toggle source

Convenience method that overrides the output of inspect

# File lib/xchange.rb, line 110
def inspect

  "#{'%.02f' % (@amount_bigdecimal)} #{@currency}"

end