replaceCharactersInRange.swift

while baseString.containsString("Hello") {
    let nsRange = baseString.rangeOfString("Hello")
    ranges.append(nsRange)
    
    var replaceString = ""
    for _ in 0..<nsRange.length {
        replaceString += "§" // secret unallowed character
    }
    baseString.replaceCharactersInRange(nsRange, withString: replaceString)
}