Index of a substring in a string with Swift

Question

I\'m used to do this in JavaScript:

var domains = \"abcde\".substring(0, \"abcde\".indexOf(\"cd\")) // Returns \"ab\"

Swift doesn\'t have t

Answer 1

Leo Dabus's answer is great. Here is my answer based on his answer using compactMap to avoid Index out of range error.

Swift 5.1

extension StringProtocol {
    func ranges(of targetString: Self, options: String.CompareOptions = [], locale: Locale? = nil) -> [Range] {

        let result: [Range] = self.indices.compactMap { startIndex in
            let targetStringEndIndex = index(startIndex, offsetBy: targetString.count, limitedBy: endIndex) ?? endIndex
            return range(of: targetString, options: options, range: startIndex..