swift 比较日期大小

        let formatter = NSDateFormatter()        formatter.dateFormat = "yyyy/MM/dd"        let date = formatter.stringFromDate(self.dateView.selectedDate)        var date1=NSDate()        var date2=NSDate()        date1 = formatter.dateFromString("\(self.starTime.titleForState(UIControlState.Normal))")!        date2 = formatter.dateFromString("\(self.endTime.titleForState(UIControlState.Normal))")!        let result:NSComparisonResult = date1.compare(date2)        if result == NSComparisonResult.OrderedDescending{            print("date2<=date1")        }