Problems while parsing date with NSRegularExpression - objective-c

Question

I'm trying to parse string with date format like MM/YY and store month and year variables.
I wrote this code and can't figure out why when I pass string like "1":
match.numberOfRanges == 3
match.rangeAtindex(2) == (9223372036854775807,0)
Here is my code (regex has only two groups, so I don't understand how number of ranges can be even theoretically more than 2).
let regex = NSRegularExpression(pattern: "^(\\d{1,2})?[\\s/]*(\\d{1,2})?", options: NSRegularExpressionOptions.allZeros, error: nil)
// Expiry date string is "1"
let match = regex?.firstMatchInString(expiryDate, options: NSMatchingOptions.allZeros, range: NSMakeRange(0, expiryDateNS.length))
if let match = match {
let monthRange = match.rangeAtIndex(1)
// next string works correct - month contains "1"
var month = expiryDateNS.substringWithRange(monthRange)
if match.numberOfRanges > 1 { // match.numberOfRanges returns 3
let yearRange = match.rangeAtIndex(2) // returns LONG_MAX as location, 0 as length
// next line will crash
expiryYear = expiryDateNS.substringWithRange(yearRange)
}
}
UPDATE
As #matt asked, I'm adding few examples here.
String "1" should be parsed and stored as month == "1" and expiryYear == ""
String "12" should be parsed and stored as month == "12" and expiryYear == ""
String "12/45" should be parsed and stored as month == "12" and expiryYear == "45"
When I'm parsing string "1" with code above match.numberOfRanges is 3 and match.rangeAtindex(2) is (9223372036854775807,0)

Answer 1

For the input string "1", the second capture group (\\d{1,2})? is matched
zero times. In that case
match.rangeAtIndex(2).location is NSNotFound (which happens to be
Int.max = 9223372036854775807).
For the input string "/12" the first capture group (\\d{1,2})? would
be matched zero times. So you have to check for this cases:
var month = ""
var year = ""
if let match = match {
let monthRange = match.rangeAtIndex(1)
if monthRange.location != NSNotFound {
month = expiryDateNS.substringWithRange(monthRange)
}
let yearRange = match.rangeAtIndex(2)
if yearRange.location != NSNotFound {
year = expiryDateNS.substringWithRange(yearRange)
}
}

Answer 2

For such a simple string and pattern, NSScanner is easier. This function gives the outputs you specified for the inputs you specified:
func analyze(s:String) -> (String,String) {
var result = ("","")
let sc = NSScanner(string: s)
var first:Int32 = 0
let ok = sc.scanInt(&first)
if ok {
result.0 = String(first)
let ok = sc.scanUpToCharactersFromSet(NSCharacterSet.decimalDigitCharacterSet(), intoString: nil)
if !sc.atEnd {
var second:Int32 = 0
let ok = sc.scanInt(&second)
if ok {
result.1 = String(second)
}
}
}
return result
}

Answer 3

So if you decide to split your string you can do as follow:
let date = "12 / 45".stringByReplacingOccurrencesOfString(" ", withString: "", options: .LiteralSearch, range: nil)
let components = date.componentsSeparatedByString("/")
let month = components.count > 0 ? components.first! : ""
let expiryYear = components.count > 1 ? components.last! : ""