Swift find all occurrences of a substring

Question

I have an extension here of the String class in Swift that returns the index of the first letter of a given substring.

Can anybody please help me make it so it will

Answer 1

I have tweaked the accepted answer so that case sensitivity can be configured

extension String {
    func allIndexes(of subString: String, caseSensitive: Bool = true) -> [Int] {
        let subString = caseSensitive ? subString : subString.lowercased()
        let mainString = caseSensitive ? self : self.lowercased()
        var indices = [Int]()
        var searchStartIndex = mainString.startIndex
        while searchStartIndex < mainString.endIndex,
            let range = mainString.range(of: subString, range: searchStartIndex..