Add Money.with_bank for Dynamic Currency Stores

lib/money-rails/money.rb

@@ -5,6 +5,19 @@ class Money
   class << self
     alias_method :orig_default_formatting_rules, :default_formatting_rules
 
+    # Temporarily sets the default bank for Money operations within the block
+    #
+    # @param bank [Money::Bank] the bank to use temporarily
+    # @yield the block to execute with the temporary bank
+    # @return [Object] the return value of the yielded block
+    #
+    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 +142,29 @@
         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