let a:Int?=Int(firstText.text)// firstText is UITextField
let b:Int?=Int(secondText.text)// secondText is UITextField
from：http://stackoverflow.com/questions/24115141/swift-converting-string-to-int/30773127#30773127
let a:Int?=Int(firstText.text)// firstText is UITextField
let b:Int?=Int(secondText.text)// secondText is UITextField
from：http://stackoverflow.com/questions/24115141/swift-converting-string-to-int/30773127#30773127
