ios - 将 String 转换为 NSDate 但仍然无法访问 dateByAddingTimeInterval 方法

Question

   @IBAction func onDateChanged(sender: AnyObject) {
    let dateFormatter = NSDateFormatter()
    
   // dateFormatter.dateStyle = NSDateFormatterStyle.ShortStyle
    dateFormatter.timeStyle = NSDateFormatterStyle.ShortStyle
    
    let strDate = dateFormatter.stringFromDate(datePicker.date)
    
    let timeinterval = NSTimeInterval.abs(17 * 60) //time in seconds
    let newDate = strDate.dateByAddingTimeInterval(-timeinterval)
    // ERROR =- on the above line I get an error saying that type String does not have a method called dateByAddingTimeInterval, however I made the string a NSDate value in the variable newDate.

    
    print("\(strDate) is the date on the datePicker @")
}

正如你所看到的，我在第 7 行中清楚地将日期选择器的字符串值转换为 NSDate，但它仍然不允许我使用 dateByAddingTimeInterval 方法，因为它仍然认为它是一个字符串.

Answer 1

看来您所做的与您认为的相反。 dateFormatter.stringFromDate(datePicker.date) 将 NSDate 转换为 String。如果这是您的意图，您应该在将日期转换为 String 之前将时间间隔添加到日期中。就像这样。

let timeinterval = NSTimeInterval.abs(17 * 60) //time in seconds
let newDate = datePicker.date.dateByAddingTimeInterval(-timeinterval)
let strDate = dateFormatter.stringFromDate(newDate)
print("\(strDate) is the date on the datePicker @")