Swift Get string between 2 strings in a string

Question

I am getting a string from html parse that is;

string = "javascript:getInfo(1,'Info/99/something', 'City Hall',1, 99);"

my code is something like

var startIndex = text.rangeOfString("'")
var endIndex = text.rangeOfString("',")
var range2 = startIndex2...endIndex
substr= string.substringWithRange(range)

i am not sure if my second splitting string should be "'" or "',"

i want my outcome as

substr = "Info/99/something"

Solution 1

I'd use a regular expression to extract substrings from complex input like this.

Swift 3.1:

let test = "javascript:getInfo(1,'Info/99/something', 'City Hall',1, 99);"

if let match = test.range(of: "(?<=')[^']+", options: .regularExpression) {
    print(test.substring(with: match))
}

// Prints: Info/99/something

Swift 2.0:

let test = "javascript:getInfo(1,'Info/99/something', 'City Hall',1, 99);"

if let match = test.rangeOfString("(?<=')[^']+", options: .RegularExpressionSearch) {
    print(test.substringWithRange(match))
}

// Prints: Info/99/something

Solution 2

extension String {
    
    func slice(from: String, to: String) -> String? {
        return (range(of: from)?.upperBound).flatMap { substringFrom in
            (range(of: to, range: substringFrom..<endIndex)?.lowerBound).map { substringTo in
                String(self[substringFrom..<substringTo])
            }
        }
    }
}

"javascript:getInfo(1,'Info/99/something', 'City Hall',1, 99);"
  .sliceFrom("'", to: "',")

Solution 3

In Swift 4 or later you can create an extension method on StringProtocol to support substrings as well. You can just return a Substring instead of a new String:

edit/update: Swift 5 or later

extension StringProtocol  {
    func substring<S: StringProtocol>(from start: S, options: String.CompareOptions = []) -> SubSequence? {
        guard let lower = range(of: start, options: options)?.upperBound
        else { return nil }
        return self[lower...]
    }
    func substring<S: StringProtocol>(through end: S, options: String.CompareOptions = []) -> SubSequence? {
        guard let upper = range(of: end, options: options)?.upperBound
        else { return nil }
        return self[..<upper]
    }
    func substring<S: StringProtocol>(upTo end: S, options: String.CompareOptions = []) -> SubSequence? {
        guard let upper = range(of: end, options: options)?.lowerBound
        else { return nil }
        return self[..<upper]
    }
    func substring<S: StringProtocol, T: StringProtocol>(from start: S, upTo end: T, options: String.CompareOptions = []) -> SubSequence? {
        guard let lower = range(of: start, options: options)?.upperBound,
            let upper = self[lower...].range(of: end, options: options)?.lowerBound
        else { return nil }
        return self[lower..<upper]
    }
    func substring<S: StringProtocol, T: StringProtocol>(from start: S, through end: T, options: String.CompareOptions = []) -> SubSequence? {
        guard let lower = range(of: start, options: options)?.upperBound,
            let upper = self[lower...].range(of: end, options: options)?.upperBound
        else { return nil }
        return self[lower..<upper]
    }
}

---

Usage:

let string = "javascript:getInfo(1,'Info/99/something', 'City Hall',1, 99);"
let substr = string.substring(from: "'")                   // "Info/99/something', 'City Hall',1, 99);"
let through = string.substring(through: "Info")  // "javascript:getInfo"
let upTo = string.substring(upTo: "Info")  // "javascript:get"
let fromUpTo = string.substring(from: "'", upTo: "',")  // "Info/99/something"
let fromThrough = string.substring(from: "'", through: "',")  // "Info/99/something',"

let fromUpToCaseInsensitive = string.substring(from: "'info/", upTo: "/something", options: .caseInsensitive)  // "99"

Solution 4

Consider using a regular expression to match everything between single quotes.

let string = "javascript:getInfo(1,'Info/99/something', 'City Hall',1, 99);"

let pattern = "'(.+?)'"
let regex = NSRegularExpression(pattern: pattern, options: nil, error: nil)
let results = regex!.matchesInString(string, options: nil, range: NSMakeRange(0, count(string)))  as! [NSTextCheckingResult]

let nsstring = string as NSString
let matches = results.map { result in return nsstring.substringWithRange(result.range)}

// First match
println(matches[0])

View more solutions

Comments

[CodyMace]

This is awesome! Thanks!

[Makaille]

@oisdk does it work if we need to slice from a string to the end of the string ? Ex : "blabla popo titi toto" -> slice(from "popo", to : endOfString) ?

[Chameleon]

amazing and simple

[Martin R]

In Swift 4 you can also compute the second range as self[substringFrom...].range(of: to), that saves some keystrokes and the mention of endIndex.

[pkamb]

I found this return flatmap.().map() code pretty hard to grok for the function; so I tried rewriting a version using guard.

[bshirley]

For more detail on the regex, see stackoverflow.com/questions/6109882/…

[Mendy]

@Makaille see this answer