Convert NSDate to String in iOS Swift [duplicate]

问题:

This question already has an answer here:

• Convert NSDate to NSString 13 answers

I am trying to convert a NSDate to a String and then Change Format. But when I pass NSDate to String it is producing whitespace.

 let formatter = DateFormatter()
 let myString = (String(describing: date))
 formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
 let yourDate: Date? = formatter.date(from: myString)
 formatter.dateFormat = "dd-MMM-yyyy"
 print(yourDate)

回答1:

you get the detail information from Apple Dateformatter Document.If you want to set the dateformat for your dateString, see this link , the detail dateformat you can get here for e.g , do like

let formatter = DateFormatter()
// initially set the format based on your datepicker date / server String
formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"

let myString = formatter.string(from: Date()) // string purpose I add here 
// convert your string to date
let yourDate = formatter.date(from: myString)
//then again set the date format whhich type of output you need
formatter.dateFormat = "dd-MMM-yyyy"
// again convert your date to string
let myStringafd = formatter.string(from: yourDate!)

print(myStringafd)

you get the output as

回答2:

I always use this code while converting Date to String . (Swift 3)

extension Date
{
    func toString( dateFormat format  : String ) -> String
    {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = format
        return dateFormatter.string(from: self)
    }

}

and call like this . .

let today = Date()
today.toString(dateFormat: "dd-MM")

回答3:

DateFormatter has some factory date styles for those too lazy to tinker with formatting strings. If you don't need a custom style, here's another option:

extension Date {  
  func asString(style: DateFormatter.Style) -> String {
    let dateFormatter = DateFormatter()
    dateFormatter.dateStyle = style
    return dateFormatter.string(from: self)
  }
}

This gives you the following styles:

short, medium, long, full

Example usage:

let myDate = Date()
myDate.asString(style: .full)   // Wednesday, January 10, 2018
myDate.asString(style: .long)   // January 10, 2018
myDate.asString(style: .medium) // Jan 10, 2018
myDate.asString(style: .short)  // 1/10/18

回答4:

Your updated code.update it.

let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
let myString = formatter.string(from: date as Date)
let yourDate: Date? = formatter.date(from: myString)
formatter.dateFormat = "dd-MMM-yyyy"
print(yourDate!)

回答5:

Something to keep in mind when creating formatters is to try to reuse the same instance if you can, as formatters are fairly computationally expensive to create. The following is a pattern I frequently use for apps where I can share the same formatter app-wide, adapted from NSHipster.

extension DateFormatter {

    static var sharedDateFormatter: DateFormatter = {
        let dateFormatter = DateFormatter()   
        // Add your formatter configuration here     
        dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
        return dateFormatter
    }()
}

Usage:

let dateString = DateFormatter.sharedDateFormatter.string(from: Date())

回答6:

You can use this extension:

extension Date {

    func toString(withFormat format: String) -> String {
        let formatter = DateFormatter()
        formatter.dateFormat = format
        let myString = formatter.string(from: self)
        let yourDate = formatter.date(from: myString)
        formatter.dateFormat = format

        return formatter.string(from: yourDate!)
    }
}

And use it in your view controller like this (replace <"yyyy"> with your format):

yourString = yourDate.toString(withFormat: "yyyy")

回答7:

After allocating DateFormatter you need to give the formatted string then you can convert as string like this way

var date = Date()
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
let myString = formatter.string(from: date)
let yourDate: Date? = formatter.date(from: myString)
formatter.dateFormat = "dd-MMM-yyyy"
let updatedString = formatter.string(from: yourDate!)
print(updatedString)

OutPut

01-Mar-2017