在 iOS Swift 中将 NSDate 转换为 String

我试图转换一个 NSDate到一个 String，然后改变格式。但是当我将 NSDate传递给 String时，它会产生空格。

 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)
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最佳答案

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 myStringDate = formatter.string(from: yourDate!)


print(myStringDate)

you get the output as

enter image description here

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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!)
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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

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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")
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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")
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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())
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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

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