试试这个：

对于旧版的swift：

For older swift:

var a : String = "Cash"
var b  : String = "cash"

if(a.caseInsensitiveCompare(b) == NSComparisonResult.OrderedSame){
    println("voila")
}

Swift 3.0

Swift 3.0

if(a.caseInsensitiveCompare(b) == ComparisonResult.orderedSame){
        print("voila")
}