import Foundation
let pattern = #"<\/?(\d)"#
let regex = try! NSRegularExpression(pattern: pattern)
let testString = #"""
<?xml version="1.0"?>
<data>
<client_name>Awesome Client</client_name>
<account_number/>
<date_created>02/12/2016</date_created>
<form_number>4126</form_number>
<customer_po/>
<terms_name>Credit Card</terms_name>
<date_shipped>12/31/1969</date_shipped>
<billing_contact_email/>
<billing_contact_address_line_1/>
<billing_contact_address_line_2/>
<billing_contact_address_line_3/>
<billing_contact_address_line_4/>
<billing_contact_address_city/>
<billing_contact_address_state>British Columbia</billing_contact_address_state>
<billing_contact_address_postal/>
<billing_contact_address_country>Canada</billing_contact_address_country>
<shipping_contact_address_line_1/>
<shipping_contact_address_line_2/>
<shipping_contact_address_line_3/>
<shipping_contact_address_line_4/>
<shipping_contact_address_city/>
<shipping_contact_address_state>British Columbia</shipping_contact_address_state>
<shipping_contact_address_postal/>
<shipping_contact_address_country>Canada</shipping_contact_address_country>
<billing_contact_first_name>another</billing_contact_first_name>
<billing_contact_last_name>client</billing_contact_last_name>
<client_rep_full_name>Rob Montebelli</client_rep_full_name>
<order_rep_full_name>Mark Graham</order_rep_full_name>
<job_name>77777</job_name>
<job_number>2620</job_number>
<event_type>Donor Gift</event_type>
<due_date>02/12/2016</due_date>
<shipping_method/>
<currency>CAD</currency>
<total_taxes>0.00</total_taxes>
<total_subtotal>1,760.16</total_subtotal>
<total>1,760.16</total>
<items>
<item0>
<taxes>
<0>E</0>
</taxes>
<title>1889-24</title>
<quantity>6</quantity>
<description>Carhartt (R) Signature Utility Duffel; TBD TBD</description>
<unit_price>159.32</unit_price>
</item0>
<item1>
<taxes>
<0>E</0>
</taxes>
<title>0022-56</title>
<quantity>12</quantity>
<description>Zoom (TM) DayTripper Sling Compu-Messenger; TBD TBD</description>
<unit_price>67.02</unit_price>
</item1>
</items>
</data>
"""#
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let substitutionString = #"<number$1"#
let result = regex.stringByReplacingMatches(in: testString, range: stringRange, withTemplate: substitutionString)
print(result)
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Swift 5.2, please visit: https://developer.apple.com/documentation/foundation/nsregularexpression