gistfile1.swift

var cardNumber = ""
var cvv = ""
var expirationMonth = 0
var expirationYear = 0

var showError:(String)->Void = { errorMsg in
    let alert = UIAlertView(title: "Missing Information", message: "Please ensure your \(errorMsg) is correct", delegate: nil, cancelButtonTitle: "OK")
    alert.show()

}

var ok = false
if let tn = txtCardNumber {
    cardNumber = tn.cardNumber
    if cardNumber.utf16Count >= 13 { ok = true }
}

if !ok {
    showError("credit card number")
    return false
}

ok = false
if let tc = txtSecurityCode {
    cvv = tc.text
    if cvv.utf16Count >= 3 { ok = true }
}
if !ok {
    showError("security code")
    return false
}

ok = false
if let lm = lblExpirationMonth {
    if let t = lm.text {
        if let em = t.substringToIndex(advance(t.startIndex, 2)).toInt() {
            expirationMonth = em
            ok = true
        }
    }
}

if !ok {
    showError("expiration date - month")
    return false
}

ok = false
if let ly = lblExpirationYear {
    if let t = ly.text {
        if let ey = t.toInt() {
            expirationYear = ey
            ok = true
        }
    }
}

if !ok {
    showError("expiration date - year")
    return false
}

if let p = purchase {
    p.creditCardInfo = GCICreditCardInfo(cardNumber: cardNumber,
        cvv: cvv,
        expirationMonth: expirationMonth,
        expirationYear: expirationYear)
}