问题
In a swift playground, I have been using
NSDate.date()
But, this always appears with the time element appended. For my app I need to ignore the time element. Is this possible in Swift? How can it be done? Even if I could set the time element to be the same time on every date that would work too.
Also, I am trying to compare two dates and at the moment I am using the following code:
var earlierDate:NSDate = firstDate.earlierDate(secondDate)
Is this the only way or can I do this in a way that ignores the time element? For instance I don\'t want a result if they are the same day, but different times.
回答1:
Use this Calendar function to compare dates in iOS 8.0+
func compare(_ date1: Date, to date2: Date, toGranularity component: Calendar.Component) -> ComparisonResult
passing .day as the unit
Use this function as follows:
let now = Date()
// "Sep 23, 2015, 10:26 AM"
let olderDate = Date(timeIntervalSinceNow: -10000)
// "Sep 23, 2015, 7:40 AM"
var order = Calendar.current.compare(now, to: olderDate, toGranularity: .hour)
switch order {
case .orderedDescending:
print("DESCENDING")
case .orderedAscending:
print("ASCENDING")
case .orderedSame:
print("SAME")
}
// Compare to hour: DESCENDING
var order = Calendar.current.compare(now, to: olderDate, toGranularity: .day)
switch order {
case .orderedDescending:
print("DESCENDING")
case .orderedAscending:
print("ASCENDING")
case .orderedSame:
print("SAME")
}
// Compare to day: SAME
回答2:
There are several useful methods in NSCalendar in iOS 8.0+:
startOfDayForDate, isDateInToday, isDateInYesterday, isDateInTomorrow
And even to compare days:
func isDate(date1: NSDate!, inSameDayAsDate date2: NSDate!) -> Bool
To ignore the time element you can use this:
var toDay = Calendar.current.startOfDay(for: Date())
But, if you have to support also iOS 7, you can always write an extension
extension NSCalendar {
func myStartOfDayForDate(date: NSDate!) -> NSDate!
{
let systemVersion:NSString = UIDevice.currentDevice().systemVersion
if systemVersion.floatValue >= 8.0 {
return self.startOfDayForDate(date)
} else {
return self.dateFromComponents(self.components(.CalendarUnitYear | .CalendarUnitMonth | .CalendarUnitDay, fromDate: date))
}
}
}
回答3:
I wrote the following method to compare two dates by borrowing from Ashley Mills solution. It compares two dates and returns true if the two dates are the same (stripped of time).
func compareDate(date1:NSDate, date2:NSDate) -> Bool {
let order = NSCalendar.currentCalendar().compareDate(date1, toDate: date2,
toUnitGranularity: .Day)
switch order {
case .OrderedSame:
return true
default:
return false
}
}
And it is called like this:
if compareDate(today, date2: anotherDate) {
// The two dates are on the same day.
}
回答4:
In Swift 4:
func compareDate(date1:Date, date2:Date) -> Bool {
let order = NSCalendar.current.compare(date1, to: date2, toGranularity: .day)
switch order {
case .orderedSame:
return true
default:
return false
}
}
回答5:
Two Dates comparisions in swift.
// Date comparision to compare current date and end date.
var dateComparisionResult:NSComparisonResult = currentDate.compare(endDate)
if dateComparisionResult == NSComparisonResult.OrderedAscending
{
// Current date is smaller than end date.
}
else if dateComparisionResult == NSComparisonResult.OrderedDescending
{
// Current date is greater than end date.
}
else if dateComparisionResult == NSComparisonResult.OrderedSame
{
// Current date and end date are same.
}
回答6:
For iOS7 support
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd"
let date1String = dateFormatter.stringFromDate(date1)
let date2String = dateFormatter.stringFromDate(date2)
if date1String == date2String {
println("Equal date")
}
回答7:
You can compare two dates using it's description.
let date1 = NSDate()
let date2 = NSDate(timeIntervalSinceNow: 120)
if date1.description == date2.description {
print(true)
} else {
print(false) // false (I have added 2 seconds between them)
}
If you want set the time element of your dates to a different time you can do as follow:
extension NSDate {
struct Calendar {
static let gregorian = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
}
var day: Int { return Calendar.gregorian.component(.Day, fromDate: self) }
var month: Int { return Calendar.gregorian.component(.Month, fromDate: self) }
var year: Int { return Calendar.gregorian.component(.Year, fromDate: self) }
var noon: NSDate {
return Calendar.gregorian.dateWithEra(1, year: year, month: month, day: day, hour: 12, minute: 0, second: 0, nanosecond: 0)!
}
}
let date1 = NSDate()
let date2 = NSDate(timeIntervalSinceNow: 120)
print(date1.noon == date2.noon) // true
or you can also do it using NSDateFormatter:
extension NSDate {
struct Date {
static let formatterYYYYMMDD: NSDateFormatter = {
let formatter = NSDateFormatter()
formatter.dateFormat = "yyyyMMdd"
return formatter
}()
}
var yearMonthDay: String {
return Date.formatterYYYYMMDD.stringFromDate(self)
}
func isSameDayAs(date:NSDate) -> Bool {
return yearMonthDay == date.yearMonthDay
}
}
let date1 = NSDate()
let date2 = NSDate(timeIntervalSinceNow: 120)
print(date1.yearMonthDay == date2.yearMonthDay) // true
print(date1.isSameDayAs(date2)) // true
Another option (iOS8+) is to use calendar method isDate(inSameDayAsDate:):
extension NSDate {
struct Calendar {
static let gregorian = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
}
func isInSameDayAs(date date: NSDate) -> Bool {
return Calendar.gregorian.isDate(self, inSameDayAsDate: date)
}
}
let date1 = NSDate()
let date2 = NSDate(timeIntervalSinceNow: 120)
if date1.isInSameDayAs(date: date2 ){
print(true) // true
} else {
print(false)
}
回答8:
For Swift3
var order = NSCalendar.current.compare(firstDate, to: secondDate, toGranularity: .hour)
if order == .orderedSame {
//Both the dates are same.
//Your Logic.
}
回答9:
Swift 3
let order = NSCalendar.current.compare(date1, to: date2, toGranularity: .day)
if order == .orderedAscending {
// date 1 is older
}
else if order == .orderedDescending {
// date 1 is newer
}
else if order == .orderedSame {
// same day/hour depending on granularity parameter
}
回答10:
I wrote a Swift 4 extension for comparing two dates:
import Foundation
extension Date {
func isSameDate(_ comparisonDate: Date) -> Bool {
let order = Calendar.current.compare(self, to: comparisonDate, toGranularity: .day)
return order == .orderedSame
}
func isBeforeDate(_ comparisonDate: Date) -> Bool {
let order = Calendar.current.compare(self, to: comparisonDate, toGranularity: .day)
return order == .orderedAscending
}
func isAfterDate(_ comparisonDate: Date) -> Bool {
let order = Calendar.current.compare(self, to: comparisonDate, toGranularity: .day)
return order == .orderedDescending
}
}
Usage:
startDate.isSameDateAs(endDate) // returns a true or false
回答11:
Swift:
extension NSDate {
/**
Compares current date with the given one down to the seconds.
If date==nil, then always return false
:param: date date to compare or nil
:returns: true if the dates has equal years, months, days, hours, minutes and seconds.
*/
func sameDate(date: NSDate?) -> Bool {
if let d = date {
let calendar = NSCalendar.currentCalendar()
if NSComparisonResult.OrderedSame == calendar.compareDate(self, toDate: d, toUnitGranularity: NSCalendarUnit.SecondCalendarUnit) {
return true
}
}
return false
}
}
回答12:
Swift 4
func compareDate(date1:Date, date2:Date) -> Bool {
let order = Calendar.current.compare(date1, to: date2,toGranularity: .day)
switch order {
case .orderedSame:
return true
default:
return false
}
}
回答13:
When you NSDate.date() in the playground, you see the default description printed. Use NSDateFormatter to print a localized description of the date object, possibly with only the date portion.
To zero out specific portions of a date (for the sake of comparison), use NSDateComponents in conjunction with NSCalendar.
回答14:
In my experience, most people's problems with using NSDate comes from the incorrect assumption that an NSDate can be used to represent a date in the 'normal' sense (i.e. a 24 period starting at midnight in the local timezone). In normal (everyday / non-programming) usage, 1st January 2014 in London is the same date as 1st January in Beijing or New York even though they cover different periods in real time. To take this to the extreme, the time on Christmas Island is UTC+14 while the time on Midway Island is UTC-11. So 1st January 2014 on these two island are the same date even though one doesn't even start until the other has been completed for an hour.
If that is the kind of date you are recording (and if you are not recording the time component, it probably is), then do not use NSDate (which stores only seconds past 2001-01-01 00:00 UTC, nothing else) but store the year month and day as integers - perhaps by creating your own CivilDate class that wraps these values - and use that instead.
Only dip into NSDate to compare dates and then make sure to explicitly declare the time zone as "UTC" on both NSDates for comparison purposes.
回答15:
Swift iOS 8 and up When you need more than simply bigger or smaller date comparisons. For example is it the same day or the previous day,...
extension Date {
func compareTo(date: Date, toGranularity: Calendar.Component ) -> ComparisonResult {
var cal = Calendar.current
cal.timeZone = TimeZone(identifier: "Europe/Paris")!
return cal.compare(self, to: date, toGranularity: toGranularity)
}
}
For examples how to use this in a filter see this answer:
https://stackoverflow.com/a/45746206/4946476
回答16:
To answer your question:
Is this possible in Swift?
Yes, it is possible
Ahh, you also want to now HOW
let cal = NSCalendar.currentCalendar()
cal.rangeOfUnit(.DayCalendarUnit, startDate: &d1, interval: nil, forDate: d1) // d1 NSDate?
cal.rangeOfUnit(.DayCalendarUnit, startDate: &d2, interval: nil, forDate: d2) // d2 NSDate?
Now d1 and d2 will contain the dates at beginning of their days.
compare with d1!.compare(d2!)
To display them without time portion, us NSDateFormatter.
来源：https://stackoverflow.com/questions/24577087/comparing-nsdates-without-time-component