Add Money.with_bank for Dynamic Currency Stores

README.md

@@ -385,6 +385,29 @@ t = Transaction.new(amount_cents: 2500, currency: "CAD")
 t.amount == Money.new(2500, "CAD") # true
 ```
 
+####  Assigning Currencies on the go
+
+If you would like to assign different Currency stores(banks) on the go you can use the following method:
+
+`Money.with_bank(bank_of_america)`
+
+This is to allow the usage of custom currency stores to be loaded per User sessions.
+
+An example would be to use the following in a certain controller
+
+```ruby
+class ApplicationController
+  around_action :currency_store
+  def currency_store
+    Money.with_bank(Money::Bank::VariableExchange.new(MyCustomStore.new)) do
+      # Rate will be loaded from the current_user setup.
+      Money.add_rate("USD", "EUR", 0.5)
+      yield
+    end
+  end
+end
+```
+
 ### Configuration parameters
 
 You can handle a bunch of configuration params through ```money.rb``` initializer:

lib/money-rails/money.rb

@@ -5,6 +5,13 @@ class Money
   class << self
     alias_method :orig_default_formatting_rules, :default_formatting_rules
 
+    def with_bank(bank)
+      old_bank, ::Money.default_bank = ::Money.default_bank, bank
+      yield
+    ensure
+      ::Money.default_bank = old_bank
+    end
+
     def default_formatting_rules
       rules = orig_default_formatting_rules || {}
       defaults = {

spec/configuration_spec.rb

@@ -142,6 +142,30 @@
         end
       end
     end
+  end
+
+  describe 'modifying default bank from memory' do
+    it 'creates new banks when needed' do
+      old_bank = Money.default_bank
+
+      bank = Money::Bank::VariableExchange.new
+
+      Money.with_bank(bank) {}
+      expect(Money.default_bank).to eq(old_bank)
+    end
+
+    it "uses the correct bank inside block" do
+      old_bank = Money.default_bank
+      custom_store = double
+      bank = Money::Bank::VariableExchange.new(custom_store)
+      Money.with_bank(bank) do
+        expect(custom_store).to receive(:add_rate).with("USD", "EUR", 0.5).once
+        Money.add_rate("USD", "EUR", 0.5)
+      end
 
+      expect(old_bank).to receive(:add_rate)
+      Money.add_rate("USD", "EUR", 0.5)
+    end
   end
-end
+
+end