Regex.swift

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install

Use CocoaPods.

Add to your Podfile:

pod 'Regex'

And then run pod install from the shell:

$ pod install

usage

Simple use cases: String extension methods

String.grep()

This method is modeled after Javascript’s String.match(). It returns a Regex.MatchResult object. The object’s captures property is an array of Strings much as one would expect from its Javascript equivalent.

let result = "Winnie the Pooh".grep("\\s+([a-z]+)\\s+")

result.searchString == "Winnie the Pooh"
result.captures.count == 2
result.captures[0] == " the "
result.captures[1] == "the"
result.boolValue == true       // `boolValue` is `true` if there were more than 0 matches

// You can use `grep()` in conditionals because of the `boolValue` property its result exposes
let emailAddress = "bryn&typos.org"
if !emailAddress.grep("@") {
    // that's not an email address!
}

String.replaceRegex()

This method is modeled after the version of Javascript’s String.replace() that accepts a Regex parameter. 

let name = "Winnie the Pooh"
let darkName = name.replaceRegex("Winnie the ([a-zA-Z]+)", with: "Darth $1")
// darkName == "Darth Pooh"

Advanced use cases: Regex object and operators

operator =~

You can use the =~ operator to search a String (the left operand) for a Regex (the right operand). It’s the same as calling theString.grep("the regex pattern"), but might be more clear in some cases. It returns the same Regex.MatchResult object as String.grep().

"Winnie the Pooh" =~ Regex("\\s+(the)\\s+")  // returns a Regex.MatchResult

Quickly loop over a Regex’s captures:

for capture in ("Winnie the Pooh" =~ Regex("\\s+(the)\\s+")).captures {
    // capture is a String
}

Overriden map() function for substitution

A more functional programming way of doing string replacement is possible via an override for map(). In keeping with the overall aim to avoid reinventing a perfectly good wheel (i.e., NSRegularExpression), this function simply calls through to NSRegularExpression.replaceMatchesInString().

func map (regexResult:Regex.MatchResult, replacementTemplate:String) -> String

You can use it like so:

let stageName = map("Winnie the Pooh" =~ Regex("([a-zA-Z]+)\\s+(the)(.*)"), "$2 $1")
// stageName == "the Winnie"

Or if you have some functional operators lying around (for example: https://github.com/brynbellomy/Funky), it’s a little less wordy:

("Winnie the Pooh" =~ Regex("([a-zA-Z]+)\\s+(the)(.*)")) |> map‡("$2 $1")

… but you have to be as crazy as me to find that more readable than "Winnie".replaceRegex(_:withString:), so no pressure.

contributors / authors