ios 你如何创建一个 Swift Date 对象？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/24089999/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How do you create a Swift Date object?
提问by code_cookies
How do you create a date object from a date in swift xcode.
如何从 swift xcode 中的日期创建日期对象。
eg in javascript you would do:
var day = new Date('2014-05-20');
例如在 javascript 中你会这样做：
var day = new Date('2014-05-20');
回答by Suragch
Swift has its own Datetype. No need to use NSDate.
Swift 有自己的Date类型。无需使用NSDate.
Creating a Date and Time in Swift
在 Swift 中创建日期和时间
In Swift, dates and times are stored in a 64-bit floating point number measuring the number of seconds since the reference date of January 1, 2001 at 00:00:00 UTC. This is expressed in the Datestructure. The following would give you the current date and time:
在 Swift 中，日期和时间存储在一个 64 位浮点数中，用于测量自 2001 年 1 月 1 日参考日期 00:00:00 UTC以来的秒数。这体现在Date结构上。以下将为您提供当前日期和时间：
let currentDateTime = Date()
For creating other date-times, you can use one of the following methods.
要创建其他日期时间，您可以使用以下方法之一。
Method 1
方法一
If you know the number of seconds before or after the 2001 reference date, you can use that.
如果您知道 2001 年参考日期之前或之后的秒数，则可以使用它。
let someDateTime = Date(timeIntervalSinceReferenceDate: -123456789.0) // Feb 2, 1997, 10:26 AM
Method 2
方法二
Of course, it would be easier to use things like years, months, days and hours (rather than relative seconds) to make a Date. For this you can use DateComponentsto specify the components and then Calendarto create the date. The Calendargives the Datecontext. Otherwise, how would it know what time zone or calendar to express it in?
当然，使用诸如年、月、日和小时（而不是相对秒）之类的东西来制作Date. 为此，您可以使用DateComponents指定组件，然后Calendar创建日期。在Calendar给出了Date上下文。否则，它怎么知道用哪个时区或日历来表达它？
// Specify date components
var dateComponents = DateComponents()
dateComponents.year = 1980
dateComponents.month = 7
dateComponents.day = 11
dateComponents.timeZone = TimeZone(abbreviation: "JST") // Japan Standard Time
dateComponents.hour = 8
dateComponents.minute = 34
// Create date from components
let userCalendar = Calendar.current // user calendar
let someDateTime = userCalendar.date(from: dateComponents)
Other time zone abbreviations can be found here. If you leave that blank, then the default is to use the user's time zone.
其他时区缩写可以在这里找到。如果您将其留空，则默认使用用户的时区。
Method 3
方法三
The most succinct way (but not necessarily the best) could be to use DateFormatter.
最简洁的方法（但不一定是最好的）可能是使用DateFormatter.
let formatter = DateFormatter()
formatter.dateFormat = "yyyy/MM/dd HH:mm"
let someDateTime = formatter.date(from: "2016/10/08 22:31")
The Unicode technical standards show other formatsthat DateFormattersupports.
在统一的技术标准表明其他格式是DateFormatter支持的。
Notes
笔记
See my full answerfor how to display the date and time in a readable format. Also read these excellent articles:
有关如何以可读格式显示日期和时间，请参阅我的完整答案。还可以阅读这些优秀的文章：
回答by algal
This is best done using an extension to the existing NSDateclass.
这最好使用现有NSDate类的扩展来完成。
The following extension adds a new initializer which will create a date in the current locale using the date string in the format you specified.
以下扩展添加了一个新的初始化程序，它将使用您指定格式的日期字符串在当前语言环境中创建一个日期。
extension NSDate
{
convenience
init(dateString:String) {
let dateStringFormatter = NSDateFormatter()
dateStringFormatter.dateFormat = "yyyy-MM-dd"
dateStringFormatter.locale = NSLocale(localeIdentifier: "en_US_POSIX")
let d = dateStringFormatter.dateFromString(dateString)!
self.init(timeInterval:0, sinceDate:d)
}
}
Now you can create an NSDate from Swift just by doing:
现在您可以通过执行以下操作从 Swift 创建一个 NSDate：
NSDate(dateString:"2014-06-06")
Please note that this implementation does not cache the NSDateFormatter, which you might want to do for performance reasons if you expect to be creating many NSDates in this way.
请注意，此实现不会缓存 NSDateFormatter，如果您希望以NSDate这种方式创建许多s，出于性能原因，您可能希望这样做。
Please also note that this implementation will simply crash if you try to initialize an NSDateby passing in a string that cannot be parsed correctly. This is because of the forced unwrap of the optional value returned by dateFromString. If you wanted to return a nilon bad parses, you would ideally use a failible initializer; but you cannot do that now (June 2015), because of a limitation in Swift 1.2, so then you're next best choice is to use a class factory method.
另请注意，如果您尝试NSDate通过传入无法正确解析的字符串来初始化 ，则此实现将简单地崩溃。这是因为强制解包由 返回的可选值dateFromString。如果你想nil在错误的解析上返回 a ，你最好使用一个可失败的初始化程序；但是你现在不能这样做（2015 年 6 月），因为 Swift 1.2 的限制，所以你的下一个最佳选择是使用类工厂方法。
A more elaborate example, which addresses both issues, is here: https://gist.github.com/algal/09b08515460b7bd229fa.
一个解决这两个问题的更详细的例子在这里：https: //gist.github.com/algal/09b08515460b7bd229fa。
Update for Swift 5
Swift 5 更新
extension Date {
init(_ dateString:String) {
let dateStringFormatter = DateFormatter()
dateStringFormatter.dateFormat = "yyyy-MM-dd"
dateStringFormatter.locale = NSLocale(localeIdentifier: "en_US_POSIX") as Locale
let date = dateStringFormatter.date(from: dateString)!
self.init(timeInterval:0, since:date)
}
}
回答by mythz
Swift doesn't have its own Date type, but you to use the existing Cocoa NSDatetype, e.g:
Swift 没有自己的 Date 类型，但您可以使用现有的 CocoaNSDate类型，例如：
class Date {
class func from(year: Int, month: Int, day: Int) -> Date {
let gregorianCalendar = NSCalendar(calendarIdentifier: .gregorian)!
var dateComponents = DateComponents()
dateComponents.year = year
dateComponents.month = month
dateComponents.day = day
let date = gregorianCalendar.date(from: dateComponents)!
return date
}
class func parse(_ string: String, format: String = "yyyy-MM-dd") -> Date {
let dateFormatter = DateFormatter()
dateFormatter.timeZone = NSTimeZone.default
dateFormatter.dateFormat = format
let date = dateFormatter.date(from: string)!
return date
}
}
Which you can use like:
您可以像这样使用：
var date = Date.parse("2014-05-20")
var date = Date.from(year: 2014, month: 05, day: 20)
回答by Adrian
Here's how I did it in Swift 4.2:
这是我在 Swift 4.2 中的做法：
extension Date {
/// Create a date from specified parameters
///
/// - Parameters:
/// - year: The desired year
/// - month: The desired month
/// - day: The desired day
/// - Returns: A `Date` object
static func from(year: Int, month: Int, day: Int) -> Date? {
let calendar = Calendar(identifier: .gregorian)
var dateComponents = DateComponents()
dateComponents.year = year
dateComponents.month = month
dateComponents.day = day
return calendar.date(from: dateComponents) ?? nil
}
}
Usage:
用法：
let marsOpportunityLaunchDate = Date.from(year: 2003, month: 07, day: 07)
回答by Kevin Machado
According to Apple documentation
根据苹果文档
Example :
例子 ：
var myObject = NSDate()
let futureDate = myObject.dateByAddingTimeInterval(10)
let timeSinceNow = myObject.timeIntervalSinceNow
回答by Jaydip
In, Swift 3.0 you have set date object for this way.
在 Swift 3.0 中，您已经为此设置了日期对象。
extension Date
{
init(dateString:String) {
let dateStringFormatter = DateFormatter()
dateStringFormatter.dateFormat = "yyyy-MM-dd"
dateStringFormatter.locale = Locale(identifier: "en_US_POSIX")
let d = dateStringFormatter.date(from: dateString)!
self(timeInterval:0, since:d)
}
}
回答by Leon
Personally I think it should be a failable initialiser:
我个人认为它应该是一个可失败的初始化程序：
extension Date {
init?(dateString: String) {
let dateStringFormatter = DateFormatter()
dateStringFormatter.dateFormat = "yyyy-MM-dd"
if let d = dateStringFormatter.date(from: dateString) {
self.init(timeInterval: 0, since: d)
} else {
return nil
}
}
}
Otherwise a string with an invalid format will raise an exception.
否则，格式无效的字符串将引发异常。
回答by Hamsternik
According to @mythz answer, I decide to post updated version of his extension using swift3syntax.
根据@mythz 的回答，我决定使用swift3语法发布他的扩展的更新版本。
extension Date {
static func from(_ year: Int, _ month: Int, _ day: Int) -> Date?
{
let gregorianCalendar = Calendar(identifier: .gregorian)
let dateComponents = DateComponents(calendar: gregorianCalendar, year: year, month: month, day: day)
return gregorianCalendar.date(from: dateComponents)
}
}
I don't use parsemethod, but if someone needs, I will update this post.
我不使用parse方法，但如果有人需要，我会更新这篇文章。
回答by Justin Domnitz
I often have a need to combine date values from one place with time values for another. I wrote a helper function to accomplish this.
我经常需要将一个地方的日期值与另一个地方的时间值结合起来。我写了一个辅助函数来完成这个。
let startDateTimeComponents = NSDateComponents()
startDateTimeComponents.year = NSCalendar.currentCalendar().components(NSCalendarUnit.Year, fromDate: date).year
startDateTimeComponents.month = NSCalendar.currentCalendar().components(NSCalendarUnit.Month, fromDate: date).month
startDateTimeComponents.day = NSCalendar.currentCalendar().components(NSCalendarUnit.Day, fromDate: date).day
startDateTimeComponents.hour = NSCalendar.currentCalendar().components(NSCalendarUnit.Hour, fromDate: time).hour
startDateTimeComponents.minute = NSCalendar.currentCalendar().components(NSCalendarUnit.Minute, fromDate: time).minute
let startDateCalendar = NSCalendar(identifier: NSCalendarIdentifierGregorian)
combinedDateTime = startDateCalendar!.dateFromComponents(startDateTimeComponents)!
回答by Nycen
According to Apple's Data Formatting Guide
根据 Apple 的数据格式指南
Creating a date formatter is not a cheap operation. If you are likely to use a formatter frequently, it is typically more efficient to cache a single instance than to create and dispose of multiple instances. One approach is to use a static variable
创建日期格式化程序并不是一项廉价的操作。如果您可能经常使用格式化程序，则缓存单个实例通常比创建和处置多个实例更有效。一种方法是使用静态变量
And while I agree with @Leon that this should be failable initializer, when you enter seed data, we could have one that isn't failable (just like there is UIImage(imageLiteralResourceName:)).
虽然我同意 @Leon 这应该是可失败的初始化程序，但当您输入种子数据时，我们可以有一个不可失败的（就像有UIImage(imageLiteralResourceName:)）。
So here's my approach:
所以这是我的方法：
extension DateFormatter {
static let yyyyMMdd: DateFormatter = {
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd"
formatter.calendar = Calendar(identifier: .iso8601)
formatter.timeZone = TimeZone(secondsFromGMT: 0)
formatter.locale = Locale(identifier: "en_US_POSIX")
return formatter
}()
}
extension Date {
init?(yyyyMMdd: String) {
guard let date = DateFormatter.yyyyMMdd.date(from: yyyyMMdd) else { return nil }
self.init(timeInterval: 0, since: date)
}
init(dateLiteralString yyyyMMdd: String) {
let date = DateFormatter.yyyyMMdd.date(from: yyyyMMdd)!
self.init(timeInterval: 0, since: date)
}
}
And now enjoy simply calling:
现在享受简单的调用：
// For seed data
Date(dateLiteralString: "2020-03-30")
// When parsing data
guard let date = Date(yyyyMMdd: "2020-03-30") else { return nil }
