XML Schema How to Declare Price and Currency

currencyschemaxmlxsd

I'm creating an XML schema that stores information about houses.

I want to store the price and the currency.

It makes sense in my mind to declare this by having the currency as an attribute of the price element.

Also, I want to restrict the values that can be entered as the currency to pounds, euros or dollars.

EG:

<price currency="euros">10000.00</price>

So at the moment I'm declaring this in my XML Schema as:

<!-- House Price, and the currency as an attribute -->
<xs:element name="price">
    <xs:complexType>
        <xs:attribute name="currency">
            <xs:simpleType>
                <xs:restriction base="xs:string">
                    <xs:enumeration value="pounds" />
                    <xs:enumeration value="euros" />
                    <xs:enumeration value="dollars" />
                </xs:restriction>
            </xs:simpleType>
        </xs:attribute>
    </xs:complexType>
</xs:element>

The issue that I have with this:

I'm not exactly sure if this will restrict the attribute element to pounds, euros or dollars
I can't seem to specify a type on the price to a double, as I would like due to the error:

Element 'price' has both a 'type' attribute and a 'anonymous type' child. Only one of these is allowed for an element.

Should I just keep it simple and declare them as separate elements:

<price>10000.00</price>
<currency>euros</currency>

…or am I on the right path?

Best Answer

Taken from the link posted by Michael Kay and applied to your problem. (Note: Use 'decimal' type instead of 'double' to avoid precision errors.)

<xs:element name="price">
  <xs:complexType>
    <xs:simpleContent>
      <xs:extension base="xs:decimal">
        <xs:attribute name="currency" type="currencyType"/>
      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>
</xs:element>

<xs:simpleType name="currencyType">
  <xs:restriction base="xs:string">
    <xs:enumeration value="pounds"/>
    <xs:enumeration value="euros"/>
    <xs:enumeration value="dollars"/>
  </xs:restriction>
</xs:simpleType>

---- Example ----

<price currency="euros">10000.00</price>

Intl.NumberFormat

JavaScript has a number formatter (part of the Internationalization API).

// Create our number formatter.
var formatter = new Intl.NumberFormat('en-US', {
  style: 'currency',
  currency: 'USD',

  // These options are needed to round to whole numbers if that's what you want.
  //minimumFractionDigits: 0, // (this suffices for whole numbers, but will print 2500.10 as $2,500.1)
  //maximumFractionDigits: 0, // (causes 2500.99 to be printed as $2,501)
});

formatter.format(2500); /* $2,500.00 */

Use undefined in place of the first argument ('en-US' in the example) to use the system locale (the user locale in case the code is running in a browser). Further explanation of the locale code.

Here's a list of the currency codes.

Intl.NumberFormat vs Number.prototype.toLocaleString

A final note comparing this to the older .toLocaleString. They both offer essentially the same functionality. However, toLocaleString in its older incarnations (pre-Intl) does not actually support locales: it uses the system locale. So when debugging old browsers, be sure that you're using the correct version (MDN suggests to check for the existence of Intl). There isn't any need to worry about this at all if you don't care about old browsers or just use the shim.

Also, the performance of both is the same for a single item, but if you have a lot of numbers to format, using Intl.NumberFormat is ~70 times faster. Therefore, it's usually best to use Intl.NumberFormat and instantiate only once per page load. Anyway, here's the equivalent usage of toLocaleString:

(2500).toLocaleString('en-US', {
  style: 'currency',
  currency: 'USD',
}); /* $2,500.00 */

Some notes on browser support and Node.js

Browser support is no longer an issue nowadays with 98% support globally, 99% in the US and 99+% in the EU
There is a shim to support it on fossilized browsers (like Internet Explorer 8), should you really need to
Node.js before v13 only supports en-US out of the box. One solution is to install full-icu, see here for more information
Have a look at CanIUse for more information

Ruby-on-rails – the best method of handling currency/money

You'll probably want to use a DECIMAL type in your database. In your migration, do something like this:

# precision is the total number of digits
# scale is the number of digits to the right of the decimal point
add_column :items, :price, :decimal, :precision => 8, :scale => 2

In Rails, the :decimal type is returned as BigDecimal, which is great for price calculation.

If you insist on using integers, you will have to manually convert to and from BigDecimals everywhere, which will probably just become a pain.

As pointed out by mcl, to print the price, use:

number_to_currency(price, :unit => "€")
#=> €1,234.01

Best Answer

Related Solutions

Javascript – How to format numbers as currency strings

Intl.NumberFormat

Intl.NumberFormat vs Number.prototype.toLocaleString

Some notes on browser support and Node.js

Ruby-on-rails – the best method of handling currency/money

Related Topic