试试这个：

var a = "Cash"
var b = "cash"
let result: NSComparisonResult = a.compare(b, options: NSStringCompareOptions.CaseInsensitiveSearch, range: nil, locale: nil)

// You can also ignore last two parameters(thanks 0x7fffffff)
//let result: NSComparisonResult = a.compare(b, options: NSStringCompareOptions.CaseInsensitiveSearch)

结果是NSComparisonResult枚举的类型：

enum NSComparisonResult : Int {

    case OrderedAscending
    case OrderedSame
    case OrderedDescending
}

因此，您可以使用if语句：

if result == .OrderedSame {
    println("equal")
} else {
    println("not equal")
}