Allow nil to be used as a default_currency

lib/money/currency.rb

@@ -33,6 +33,9 @@ def initialize(method, currency, attribute)
  # Thrown when an unknown currency is requested.
  class UnknownCurrency < ArgumentError; end
 
+ # Thrown when currency is not provided.
+ class NoCurrency < ArgumentError; end
+
  class << self
  def new(id)
  id = id.to_s.downcase

lib/money/money.rb

@@ -156,7 +156,9 @@ def self.default_currency
  @using_deprecated_default_currency = false
  end
 
- if @default_currency.respond_to?(:call)
+ if @default_currency.nil?
+ nil
+ elsif @default_currency.respond_to?(:call)
  Money::Currency.new(@default_currency.call)
  else
  Money::Currency.new(@default_currency)
@@ -308,6 +310,8 @@ def self.from_amount(amount, currency = default_currency, options = {})
  raise ArgumentError, "'amount' must be numeric" unless Numeric === amount
 
  currency = Currency.wrap(currency) || Money.default_currency
+ raise Currency::NoCurrency, 'must be provide a currency' if currency.nil?
+
  value = amount.to_d * currency.subunit_to_unit
  new(value, currency, options)
  end
@@ -338,7 +342,7 @@ class << self
  # Money.new(100, "USD") #=> #<Money @fractional=100 @currency="USD">
  # Money.new(100, "EUR") #=> #<Money @fractional=100 @currency="EUR">
  #
- def initialize( obj, currency = Money.default_currency, options = {})
+ def initialize(obj, currency = Money.default_currency, options = {})
  # For backwards compatability, if options is not a Hash, treat it as a bank parameter
  unless options.is_a?(Hash)
  options = { bank: options }
@@ -352,6 +356,7 @@ def initialize( obj, currency = Money.default_currency, options = {})
 
  # BigDecimal can be Infinity and NaN, money of that amount does not make sense
  raise ArgumentError, 'must be initialized with a finite value' unless @fractional.finite?
+ raise Currency::NoCurrency, 'must be provide a currency' if @currency.nil?
  end
 
  # Assuming using a currency using dollars:

spec/currency_spec.rb

@@ -21,6 +21,12 @@ def unregister_foo
  end
  end
 
+ describe "NoCurrency" do
+ it "is a subclass of ArgumentError" do
+ expect(described_class::NoCurrency < ArgumentError).to be true
+ end
+ end
+
  describe ".find" do
  before { register_foo }
  after { unregister_foo }

spec/money_spec.rb

@@ -70,6 +70,21 @@
  it "should have the default currency" do
  expect(money.currency).to eq Money.default_currency
  end
+
+ context 'without a default' do
+ around do |example|
+ default_currency = Money.default_currency
+ Money.default_currency = nil
+
+ example.run
+
+ Money.default_currency = default_currency
+ end
+
+ it 'should throw an NoCurrency Error' do
+ expect { money }.to raise_error(Money::Currency::NoCurrency)
+ end
+ end
  end
 
  context 'given a currency is provided' do