Swift 4 和 Xcode 9：无法使用类型为“(NSCalendar.Unit.Type, from: NSData, to: Date?)”的参数列表调用 'dateComponents'

Question

正在尝试创建倒数计时器，但我无法解决此错误：

Cannot invoke 'dateComponents' with an argument list of type '(NSCalendar.Unit.Type, from: NSData, to: Date?)'

我的代码：

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var TimerLable: UILabel!



    let formatter = DateFormatter()
    let userCleander = Calendar.current;
    let CalenderComponent : NSCalendar.Unit = [
        NSCalendar.Unit.year,
        NSCalendar.Unit.month,
        NSCalendar.Unit.day,
        NSCalendar.Unit.hour
    ]


    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

    }
    func printTime()
    {
        formatter.dateFormat = "dd/MM/yy hh:mm a"
        let StartTime = NSData()
        let EndTime = formatter.date(from: "10/08/19 12:00 a")

        let TimeDifference = userCleander.dateComponents(NSCalendar.Unit, from: StartTime, to: EndTime)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }



}

Answer 1

导致错误的主要问题只是一个错字。 StartTime 应该是 NSDate 而不是 NSData.

如果有 Swift 本地对应项（Calendar、Date 等），基本上不要使用 NS... 类。

Swift 3+ 代码是

let formatter = DateFormatter()
let userCalendar = Calendar.current

let calendarComponents : Set<Calendar.Component> = [ .year, .month, .day, .hour]

func printTime()
{
    formatter.dateFormat = "dd/MM/yy hh:mm a"
    let startTime = Date()
    let endTime = formatter.date(from: "10/08/19 12:00 am")!

    let timeDifference = userCalendar.dateComponents(calendarComponents, from: startTime, to: endTime)
}

两个注意事项：

根据命名准则，变量名以小写字母开头
日期格式与日期字符串不匹配，创建的日期需要解包。

Swift 4 和 Xcode 9：无法使用类型为“(NSCalendar.Unit.Type, from: NSData, to: Date?)”的参数列表调用 'dateComponents'

Swift 4 and Xcode 9: Cannot invoke 'dateComponents' with an argument list of type '(NSCalendar.Unit.Type, from: NSData, to: Date?)'

xcode

timer

nstimer

swift4