如何在swift中将日期格式从dd/MM/YYYY转换为YYYY-MM-dd

Question

我厌倦了从2016年7月21日到2 016-07-21,但得到了这个日期2015-12-20
这是我试过的代码

let inputFormatter = NSDateFormatter()
inputFormatter.dateFormat = "MM/dd/YYYY"

let outputFormatter = NSDateFormatter()
outputFormatter.dateFormat = "YYYY-MM-dd"

let showDate = inputFormatter.dateFromString("07/21/2016")
let resultString = outputFormatter.stringFromDate(showDate!)

print(resultString)

如何转换？
谢谢

Answer 1

首先更改year格式化程序,yyyy而不是NSDateFormatter像这样使用两个

let inputFormatter = NSDateFormatter()
inputFormatter.dateFormat = "MM/dd/yyyy"
let showDate = inputFormatter.dateFromString("07/21/2016")
inputFormatter.dateFormat = "yyyy-MM-dd"
let resultString = inputFormatter.stringFromDate(showDate!)
print(resultString)

对于swift3

func convertDateFormater(_ date: String) -> String
    {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss z"
        let date = dateFormatter.date(from: date)
        dateFormatter.dateFormat = "yyyy-MM-dd"
        return  dateFormatter.string(from: date!)

    }

Answer 2

您可以定义如下所示的函数:

// input string should always be in format "21/07/2016" ("dd/MM/yyyy")

func formattedDateFromString(dateString: String, withFormat format: String) -> String? {

    let inputFormatter = NSDateFormatter()
    inputFormatter.dateFormat = "dd/MM/yyyy"

    if let date = inputFormatter.dateFromString(dateString) {

      let outputFormatter = NSDateFormatter()
      outputFormatter.dateFormat = format

      return outputFormatter.stringFromDate(date)
    }

    return nil
}

您可以使用上面的内容传递日期字符串的输出格式.输入格式将始终为dd/MM/yyyy.然后你按如下方式使用它:

let stringA = formattedDateFromString("21/07/2016", withFormat: "yyyy-MM-dd")
let stringB = formattedDateFromString("21/07/2016", withFormat: "MMM dd, yyyy")

NSLog("stringA: \(stringA)") // 2016-07-21
NSLog("stringB: \(stringB)") // Jul 21, 2016