Swift is there a method that gives the index of a substring inside another string

Question

Is there any existing function that looks for the index of a substring inside another string? A method like .indexOfSubstring thank does this:

let word: String = "Hey there, how are you?"

let indexOf: Int = word.indexOfSubstring("ere, how are")

println("index = " + \(indexOf))

and prints:

index = 6

More or less a duplicate of [Finding index of character in Swift String](http://stackoverflow.com/questions/24029163/finding-index-of-character-in-swift-string). – That question is about finding a *character*, but the answers work for finding strings as well. — Martin R, Nov 22 '14 at 11:08

Antonio · Accepted Answer · 2014-11-22T10:49:24.110

2

You can use the rangeOfString method:

import Foundation

let word: String = "Hey there, how are you?"

if let range = word.rangeOfString("ere, how are") {
    let index = distance(word.startIndex, range.startIndex)
    println("index = \(index)")
}

It returns a range, i.e. both sides of the searched string - just use the startIndex property.

Note that this is a method borrowed from NSString

edited Nov 22 '14 at 10:49

answered Nov 22 '14 at 09:46

Antonio

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Why it is complaining about 'String' does not have member named 'rangeOfString'? for me – Dharmesh Kheni Nov 22 '14 at 09:52
maybe it should be `range` and not `ranger`, unless it's a typo in your comment :) – Antonio Nov 22 '14 at 09:55
sry It was typing mistake and I copied your code to playground.But still getting this error – Dharmesh Kheni Nov 22 '14 at 09:57
Did you `import Cocoa` ? – vacawama Nov 22 '14 at 09:58
or `import UIKit` if in iOS, or `import Foundation` if not using UI – Antonio Nov 22 '14 at 10:01
@Antonio, you should add the info about `import Foundation`, et al to your answer. – vacawama Nov 22 '14 at 10:13
2

Note that `range.startIndex` is a `String.Index` and *not* an `Int`. I would suggest `if let range = word.rangeOfString("...") { let index = distance(word.startIndex, range.startIndex) ; println("index = \(index)") } ` . – Martin R Nov 22 '14 at 10:41
Thanks @MartinR. SO wouldn't be the same without you ;-) – Antonio Nov 22 '14 at 10:50

score 1 · Answer 2 · answered Nov 22 '14 at 22:31

There is no build in method in Swift. You will need to implement it yourself. Another implementation of this is

/// Get the start index of string
///
/// :return start index of .None if not found
public func indexOf(str: String) -> Int? {
    return self.indexOfRegex(Regex.escapeStr(str))
}

/// Get the start index of regex pattern
///
/// :return start index of .None if not found
public func indexOfRegex(pattern: String) -> Int? {
    if let range = Regex(pattern).rangeOfFirstMatch(self).toRange() {
        return range.startIndex
    }
    return .None
}

This code is from this library which has bunch of extensions for common swift types such as String https://github.com/ankurp/Dollar.swift/blob/master/Cent/Cent/String.swift#L62

You can checkout the docs on the usage http://www.dollarswift.org/#indexof-str-string-int

Swift is there a method that gives the index of a substring inside another string

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