Make currency_column and a static currency explicit arguments ins…

…tead of switching on argument type

README.md

@@ -132,11 +132,13 @@ Order.where(sub_total: Money.new(9.99, 'CAD'))
 ``` 
 
 `money_column` uses an attribute called 'currency' by default. This can be
-overridden by supplying a symbol for the column name, e.g.:
-`currency: :other_column`. If your currency is hardcoded and there is no
-column, supply the currency code as a string instead. You can use multiple
-`money_column` calls to achieve the desired effects with currency on the model
-or attribute level.
+overridden by supplying another column name, e.g.: `currency_column: :other`.
+If your currency is hardcoded and there is no column, set a falsey currency
+column and supply the currency code instead:
+`money_column :price_usd, currency_column: false, currency: 'USD'`
+
+You can use multiple `money_column` calls to achieve the desired effects with
+currency on the model or attribute level.
 
 There are no validations generated. You can add these for the specified money
 and currency attributes as you normally would for any other.

lib/money_column/active_record_hooks.rb

@@ -5,18 +5,19 @@ def self.included(base)
     end
 
     module ClassMethods
-      def money_column(*columns, currency: :currency)
-        columns = columns.flatten
+      def money_column(*columns, currency_column: :currency, currency: false)
+        raise ArgumentError, 'cannot set both currency_column and a fixed currency' if currency_column && currency
 
-        if currency.is_a?(Symbol)
+        columns = columns.flatten
+        if currency_column
           columns.each do |column|
             composed_of(
               column.to_sym,
               class_name: 'Money',
-              mapping: [[column.to_s, 'value'], [currency.to_s, 'currency']]
+              mapping: [[column.to_s, 'value'], [currency_column.to_s, 'currency']]
             )
           end
-        else
+        elsif currency
           columns.each do |column|
             composed_of(
               column.to_sym,
@@ -25,6 +26,8 @@ def money_column(*columns, currency: :currency)
               constructor: proc { |value| Money.new(value, currency) }
             )
           end
+        else
+          raise ArgumentError, 'need to set either currency_column or currency'
         end
       end
     end

spec/money_column_spec.rb

@@ -7,8 +7,8 @@ class MoneyRecord < ActiveRecord::Base
   end
 
   money_column :price
-  money_column :prix, currency: :devise
-  money_column :price_usd, currency: 'USD'
+  money_column :prix, currency_column: :devise
+  money_column :price_usd, currency_column: false, currency: 'USD'
 end
 
 class MoneyWithValidation < ActiveRecord::Base
@@ -72,6 +72,32 @@ class MoneyWithValidation < ActiveRecord::Base
     end
   end
 
+  describe 'wrong money_column currency arguments' do
+    let(:subject) do
+      class MoneyWithWrongCurrencyArguments < ActiveRecord::Base
+        self.table_name = 'money_records'
+        money_column :price, currency_column: :currency, currency: 'USD'
+      end
+    end
+
+    it 'raises an ArgumentError' do
+      expect { subject }.to raise_error(ArgumentError, 'cannot set both currency_column and a fixed currency')
+    end
+  end
+
+  describe 'missing money_column currency arguments' do
+    let(:subject) do
+      class MoneyWithMissingCurrencyArguments < ActiveRecord::Base
+        self.table_name = 'money_records'
+        money_column :price, currency_column: false, currency: false
+      end
+    end
+
+    it 'raises an ArgumentError' do
+      expect { subject }.to raise_error(ArgumentError, 'need to set either currency_column or currency')
+    end
+  end
+
   describe 'null currency and validations' do
     let(:currency) { Money::NullCurrency.new }
     let(:subject) { MoneyWithValidation.new(price: money) }