迄今为止的Swift字符串日期

Question

I read a date from UserDefaults.standard as string in the following format:

"2020-11-06T05:20:20+0100"

I try to convert this string to a date using the following code

let dateFormatter = DateFormatter()
dateFormatter.locale = Locale(identifier: "de_DE")
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZ"
let dateString: String! = UserDefaults.standard.string(forKey: "timeShared")
let date = dateFormatter.date(from: dateString)

However, the result is always nil . Using let date = dateFormatter.date(from: dateString)! explicitly causes a fatal error.

Any ideas what to do?

Answer 1

Changing the former code to

dateFormatter.dateFormat = "\"yyyy-MM-dd'T'HH:mm:ssZ\""

returns a neatly formatted date subsequently. The error was that the date read from UserDefaults included "" .

Answer 2

May be UserDefaults.standard.string(forKey: "timeShared") have no value or the value is not in string format and you are doing force unwrapping in let dateString: String! = UserDefaults.standard.string(forKey: "timeShared") let dateString: String! = UserDefaults.standard.string(forKey: "timeShared") here that making the fatal error.

Better add a conditional if, then use the dateString .

Refer the below code.

let dateFormatter = DateFormatter()
dateFormatter.locale = Locale(identifier: "de_DE")
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZ"
if let dateString: String = UserDefaults.standard.string(forKey: "timeShared") {
    let date = dateFormatter.date(from: dateString)
    print(date)
} else {
    print("Data in UserDefaults: \(UserDefaults.standard.string(forKey: "timeShared"))")
}