index

• See also: Regular Expressions
• Regex | Apple Developer Documentation
• WWDC22 Regex: Beyond the Basics

Deep Dives

• Swift Regex Deep Dive | Intro to Regular Expressions | Big Nerd Ranch
• Swift Regex with practical examples | Medium

Playgrounds

• Swift Regex.com
• RegexBuilder Generator

Overview

Regular expressions are a concise way of describing a pattern, which can help you match or extract portions of a string. You can create a Regex instance using regular expression syntax, either in a regex literal or a string.

// 'keyAndValue' is created using a regex literal
let keyAndValue = /(.+?): (.+)/
// 'simpleDigits' is created from a pattern in a string
let simpleDigits = try Regex("[0-9]+")

You can use a Regex to search for a pattern in a string or substring. Call contains(_:) to check for the presence of a pattern, or firstMatch(of:) or matches(of:) to find matches.

let setting = "color: 161 103 230"
if setting.contains(simpleDigits) {
    print("'\(setting)' contains some digits.")
}
// Prints "'color: 161 103 230' contains some digits."

When you find a match, the resulting Regex.Match type includes an output property that contains the matched substring along with any captures:

if let match = setting.firstMatch(of: keyAndValue) {
    print("Key: \(match.1)")
    print("Value: \(match.2)")
}
// Key: color
// Value: 161 103 230

When you import the RegexBuilder module, you can also create Regex instances using a clear and flexible declarative syntax. Using this style, you can combine, capture, and transform regexes, RegexBuilder types, and custom parsers.