使用扩展有清晰的代码

您可以编写一个扩展来将任何Date对象转换为任何所需的日历和格式

extension Date{
    func asString(format: String = "yy/MM/dd HH:mm",
                  for identifier: Calendar.Identifier = .persian) -> String {
        let formatter = DateFormatter()
        formatter.calendar = Calendar(identifier: identifier)
        formatter.dateFormat = format
        
        return formatter.string(from: self)
    }
}

然后这样使用它:

let now = Date()

print(now.asString())  // prints -> 00/04/18 20:25
print(now.asString(format: "yyyy/MM/dd"))  // prints -> 1400/04/18
print(now.asString(format: "MM/dd", for: .gregorian))  //  prints -> 07/09  

要了解如何指定您想要的格式字符串，请查看此链接。 关于如何格式化日期的完整参考，请参阅Apple官方日期格式化指南。

如果你在Mac OS X上，你可以这样写:

NSString* s = [[NSDate date] descriptionWithCalendarFormat:@"%Y_%m_%d_%H_%M_%S" timeZone:nil locale:nil];

但是这在iOS上是不可用的。

只需添加这个扩展:

extension NSDate {
    var stringValue: String {
        let formatter = NSDateFormatter()
        formatter.dateFormat = "yourDateFormat"
        return formatter.stringFromDate(self)
    }
}

  NSDateFormatter *dateformate=[[NSDateFormatter alloc]init];
  [dateformate setDateFormat:@"yyyy"]; // Date formater
  NSString *date = [dateformate stringFromDate:[NSDate date]]; // Convert date to string
  NSLog(@"date :%@",date);

迅速回答

static let dateformat: String = "yyyy-MM-dd'T'HH:mm:ss"
public static func stringTodate(strDate : String) -> Date
{

    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = dateformat
    let date = dateFormatter.date(from: strDate)
    return date!
}
public static func dateToString(inputdate : Date) -> String
{

    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = dateformat
    return formatter.string(from: inputdate)

}

网络上有很多NSDate的助手，我倾向于使用:

https://github.com/billymeltdown/nsdate-helper/

自述摘录如下:

  NSString *displayString = [NSDate stringForDisplayFromDate:date];

这将产生以下类型的输出:

‘3:42 AM’ – if the date is after midnight today
‘Tuesday’ – if the date is within the last seven days
‘Mar 1’ – if the date is within the current calendar year
‘Mar 1, 2008’ – else ;-)