RegEx is a thin NSRegularExpression wrapper for easier regular expression testing, data extraction, and replacement in Swift.
- Test if a string matches the expression with
test() - Determine the number of matches in a string with
numberOfMatches(in:) - Retrieve all matches in a string with
matches(in:) - Retrieve the first match without processing all matches with
firstMatch(in:) - Efficiently iterate over matches with
iterator()andnext() - Replace matches with a template (including capture groups)
- Replace matches one by one with custom replacement logic in a closure
The resulting Match structure contains the full match, any captured groups, and corresponding
Swift string ranges.
By using Range<String.Index> and Substring, RegEx.Match is able to return all this information without
duplicating data from the input string 👏
Given a string:
let str = "16^32=2^128"Define an expression, for example to identify exponent notation (^) while
capturing exponent values:
let expression = "\\d+\\^(\\d+)"Use the regular expression:
let regex = try RegEx(pattern: expression)
regex.test(str) // true
regex.numberOfMatches(in: str) // 2
let first = regex.firstMatch(in: str) // 1 match with 1 captured group
first?.values // ["16^32", "32"]
let matches = regex.matches(in: str) // 2 matches with 1 captured group each
matches[0].values // ["16^32", "32"]
matches[1].values // ["2^128", "128"]let iterator = regex.iterator(for: str) // Iterate over matches one by one
iterator.next()?.values // ["16^32", "32"]
iterator.next()?.values // ["2^128", "128"]
iterator.next() // nillet regex = try RegEx(pattern: #"(\d)(\d)"#)
let result = regex.replaceMatches(in: "1234", withTemplate: "$2$1")
// result: 2143let regex = try RegEx(pattern: #"(\w+)\b"#)
let result = regex.replaceMatches(in: "Hello world!") { match in
let value = String(match.values[0] ?? "")
return String(value.reversed())
}
// result: olleH dlrow!No frameworks, just copy and paste!
public class RegEx {
private let regex: NSRegularExpression
public init(pattern: String, options: NSRegularExpression.Options = []) throws {
regex = try NSRegularExpression(pattern: pattern, options: options)
}
public struct Match {
public let values: [Substring?]
public let ranges: [Range<String.Index>?]
}
public func numberOfMatches(in string: String, from index: String.Index? = nil) -> Int {
let startIndex = index ?? string.startIndex
let range = NSRange(startIndex..., in: string)
return regex.numberOfMatches(in: string, range: range)
}
public func firstMatch(in string: String, from index: String.Index? = nil) -> Match? {
let startIndex = index ?? string.startIndex
let range = NSRange(startIndex..., in: string)
let result = regex.firstMatch(in: string, range: range)
return result.flatMap { map(result: $0, in: string) }
}
public func matches(in string: String, from index: String.Index? = nil) -> [Match] {
let startIndex = index ?? string.startIndex
let range = NSRange(startIndex..., in: string)
let results = regex.matches(in: string, range: range)
return results.map { map(result: $0, in: string) }
}
public func test(_ string: String) -> Bool {
return firstMatch(in: string) != nil
}
func map(result: NSTextCheckingResult, in string: String) -> Match {
let ranges = (0..<result.numberOfRanges).map { index in
Range(result.range(at: index), in: string)
}
let substrings = ranges.map { $0.flatMap { string[$0] }}
return Match(values: substrings, ranges: ranges)
}
}
extension RegEx {
public class Iterator: IteratorProtocol {
let regex: RegEx
let string: String
var current: RegEx.Match?
init(regex: RegEx, string: String) {
self.regex = regex
self.string = string
current = regex.firstMatch(in: string)
}
public func next() -> RegEx.Match? {
defer {
current = current.flatMap {
let index = $0.ranges[0]?.upperBound
return self.regex.firstMatch(in: self.string, from: index)
}
}
return current
}
}
public func iterator(for string: String) -> Iterator {
return Iterator(regex: self, string: string)
}
}Actually, I love unit tests, so I made this repo a Swift package that can be imported and used with Swift Package Manager.
Add the following code to your Package.swift :
dependencies: [
.package(url: "https://github.com/eneko/RegEx.git", from: "0.1.0")
],
targets: {
.target(name: "YourTarget", dependencies: ["RegEx"])
}
If curious, you can run the tests with $ swift test or $ swift test --parallel.