How to group search regular expressions using swift - regex

Question

In regular expressions you can group different matches to easily "pattern match" a given match.
while match != nil {
match = source.rangeOfString(regex, options: .RegularExpressionSearch)
if let m = match {
result.append(source.substringWithRange(m)
source.replaceRange(m, with: "")
}
}
The above works find to find a range of the match, but it cannot tell me the group. For instance if I search for words encapsulated in "" I would like to match a "word" but quickly fetch only word
Is it possible to do so in swift?

Answer 1

Swift is pretty ugly right now with regular expressions -- let's hope for more-native support soon! The method on NSRegularExpression you want is matchesInString. Here's how to use it:
let string = "This is my \"string\" of \"words\"."
let re = NSRegularExpression(pattern: "\"(.+?)\"", options: nil, error: nil)!
let matches = re.matchesInString(string, options: nil, range: NSRange(location: 0, length: string.utf16Count))
println("number of matches: \(matches.count)")
for match in matches as [NSTextCheckingResult] {
// range at index 0: full match
// range at index 1: first capture group
let substring = (string as NSString).substringWithRange(match.rangeAtIndex(1))
println(substring)
}
Output:
number of matches: 2
string
words

Answer 2

You can use this if you want to collect the matched strings.
(My answer is derived from Nate Cooks very helpful answer.)
Updated for Swift 2.1
extension String {
func regexMatches(pattern: String) -> Array<String> {
let re: NSRegularExpression
do {
re = try NSRegularExpression(pattern: pattern, options: [])
} catch {
return []
}
let matches = re.matchesInString(self, options: [], range: NSRange(location: 0, length: self.utf16.count))
var collectMatches: Array<String> = []
for match in matches {
// range at index 0: full match
// range at index 1: first capture group
let substring = (self as NSString).substringWithRange(match.rangeAtIndex(1))
collectMatches.append(substring)
}
return collectMatches
}
}
Updated for Swift 3.0
extension String {
func regexMatches(pattern: String) -> Array<String> {
let re: NSRegularExpression
do {
re = try NSRegularExpression(pattern: pattern, options: [])
} catch {
return []
}
let matches = re.matches(in: self, options: [], range: NSRange(location: 0, length: self.utf16.count))
var collectMatches: Array<String> = []
for match in matches {
// range at index 0: full match
// range at index 1: first capture group
let substring = (self as NSString).substring(with: match.rangeAt(1))
collectMatches.append(substring)
}
return collectMatches
}}

Answer 3

how about this guys, add as extension to String? )) all matches, all groups ) self = String if you want to add not as extension then add String parameter and replace all self to your parameter :)
func matchesForRegexInTextAll(regex: String!) -> [[String]] {
do {
let regex = try NSRegularExpression(pattern: regex, options: [])
let nsString = self as NSString
var resultsFinal = [[String]]()
let results = regex.matchesInString(self,
options: [], range: NSMakeRange(0, nsString.length))
for result in results {
var internalString = [String]()
for var i = 0; i < result.numberOfRanges; ++i{
internalString.append(nsString.substringWithRange(result.rangeAtIndex(i)))
}
resultsFinal.append(internalString)
}
return resultsFinal
} catch let error as NSError {
print("invalid regex: \(error.localizedDescription)")
return []
}
}

Answer 4

All the answers provided are good, but nonetheless I am going to provide my String extension written in Swift 2.2.
Noted differences:
only use the first match
supports multiple captured groups
a more accurate function name (it is capture groups, not matches)
.
extension String {
func capturedGroups(withRegex pattern: String) -> [String]? {
var regex: NSRegularExpression
do {
regex = try NSRegularExpression(pattern: pattern, options: [])
} catch {
return nil
}
let matches = regex.matchesInString(self, options: [], range: NSRange(location:0, length: self.characters.count))
guard let match = matches.first else { return nil }
// Note: Index 1 is 1st capture group, 2 is 2nd, ..., while index 0 is full match which we don't use
let lastRangeIndex = match.numberOfRanges - 1
guard lastRangeIndex >= 1 else { return nil }
var results = [String]()
for i in 1...lastRangeIndex {
let capturedGroupIndex = match.rangeAtIndex(i)
let matchedString = (self as NSString).substringWithRange(capturedGroupIndex)
results.append(matchedString)
}
return results
}
}
To use:
// Will match "bcde"
"abcdefg".capturedGroups(withRegex: "a(.*)f")

Answer 5

Updated for Swift 4
/**
String extension that extract the captured groups with a regex pattern
- parameter pattern: regex pattern
- Returns: captured groups
*/
public func capturedGroups(withRegex pattern: String) -> [String] {
var results = [String]()
var regex: NSRegularExpression
do {
regex = try NSRegularExpression(pattern: pattern, options: [])
} catch {
return results
}
let matches = regex.matches(in: self, options: [], range: NSRange(location:0, length: self.count))
guard let match = matches.first else { return results }
let lastRangeIndex = match.numberOfRanges - 1
guard lastRangeIndex >= 1 else { return results }
for i in 1...lastRangeIndex {
let capturedGroupIndex = match.range(at: i)
let matchedString = (self as NSString).substring(with: capturedGroupIndex)
results.append(matchedString)
}
return results
}
To use:
// Will match "bcde"
"abcdefg".capturedGroups(withRegex: "a(.*)f")
Gist on github: https://gist.github.com/unshapedesign/1b95f78d7f74241f706f346aed5384ff