String extension to find the ranges of occurrences of a given string.

String+Ranges.swift

import Foundation

extension String {

    /// Finds and returns the ranges of occurrences of a given string within a given range of the `String`.
    func ranges(of searchString: String, options: CompareOptions = [], range searchRange: Range<Index>? = nil, locale: Locale? = nil) -> [Range<Index>] {
        let searchRange = searchRange ?? startIndex..<endIndex

        if let foundRange = range(of: searchString, options: options, range: searchRange, locale: locale) {
            let nextRange = foundRange.upperBound..<searchRange.upperBound
            return [foundRange] + ranges(of: searchString, options: options, range: nextRange, locale: locale)
        } else {
            return []
        }
    }
}