如何判断 NSDate 是否是今天？

Question

如何检查 NSDate 是否属于今天？

我曾经使用 [aDate description] 中的前 10 个字符进行检查。 [[aDate description] substringToIndex:10] 返回类似 "YYYY-MM-DD" 的字符串，因此我将该字符串与 [[[NSDate 返回的字符串进行比较日期] 描述] substringToIndex:10]。

有没有更快速和/或更简洁的方法来检查？

谢谢。

Answer 1

在 macOS 10.9+ 中iOS 8+，NSCalendar/Calendar 上有一个方法可以做到这一点！

- (BOOL)isDateInToday:(NSDate *)date 

所以你只需执行

Objective-C:

BOOL today = [[NSCalendar currentCalendar] isDateInToday:date];

Swift 3:

let today = Calendar.current.isDateInToday(date)

Answer 2

您可以比较日期组件：

NSDateComponents *otherDay = [[NSCalendar currentCalendar] components:NSCalendarUnitEra | NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay fromDate:aDate];
NSDateComponents *today = [[NSCalendar currentCalendar] components:NSCalendarUnitEra | NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay fromDate:[NSDate date]];
if([today day] == [otherDay day] &&
   [today month] == [otherDay month] &&
   [today year] == [otherDay year] &&
   [today era] == [otherDay era]) {
    //do stuff
}

编辑：

我更喜欢 stefan 的方法，我认为它可以使 if 语句更清晰、更易于理解：

NSCalendar *cal = [NSCalendar currentCalendar];
NSDateComponents *components = [cal components:(NSCalendarUnitEra | NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay) fromDate:[NSDate date]];
NSDate *today = [cal dateFromComponents:components];
components = [cal components:(NSCalendarUnitEra | NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay) fromDate:aDate];
NSDate *otherDate = [cal dateFromComponents:components];

if([today isEqualToDate:otherDate]) {
    //do stuff
}

克里斯，我已经采纳了您的建议。我必须查一下时代是什么，所以对于其他不知道的人来说，它区分了公元前和公元。对于大多数人来说这可能是不必要的，但它很容易检查并增加了一些确定性，所以我将其包括在内。如果您追求速度，这可能不是一个好方法。

---

注意与许多关于SO的答案一样，7年后这已经完全过时了。在 Swift 中现在只需使用 .isDateInToday

Answer 3

这是您问题的一个分支，但如果您想打印带有“今天”或“昨天”的 NSDate，请使用

- (void)setDoesRelativeDateFormatting:(BOOL)b

NSDateFormatter 的函数

Answer 4

我会尝试将今天的日期标准化为午夜，然后将第二个日期标准化为午夜，然后比较它是否是相同的 NSDate。

来自 Apple 示例 以下是如何将今天的日期标准化为午夜，对第二个日期执行相同的操作并进行比较：

NSCalendar * gregorian = [[NSCalendar alloc]
                               initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents * components =
    [gregorian components:
                 (NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit)
                 fromDate:[NSDate date]];
NSDate * today = [gregorian dateFromComponents:components];

Answer 5

Catfish_Man 建议的工作Swift 扩展：

extension Date {

    var isToday: Bool {
        Calendar.current.isDateInToday(self)
    }
    
}

Answer 6

无需处理组件、时代和其他东西。

NSCalendar 提供了一种方法来获取现有日期的特定时间单位的开始时间。

此代码将获取今天和另一个日期的开始并进行比较。如果其计算结果为 NSOrderedSame，则两个日期都在同一天 - 所以今天。

NSDate *today = nil;
NSDate *beginningOfOtherDate = nil;

NSDate *now = [NSDate date];
[[NSCalendar currentCalendar] rangeOfUnit:NSDayCalendarUnit startDate:&today interval:NULL forDate:now];
[[NSCalendar currentCalendar] rangeOfUnit:NSDayCalendarUnit startDate:&beginningOfOtherDate interval:NULL forDate:beginningOfOtherDate];

if([today compare:beginningOfOtherDate] == NSOrderedSame) {
    //otherDate is a date in the current day
}

Answer 7

extension NSDate {
  func isToday() -> Bool {
    let cal = NSCalendar.currentCalendar()
    var components = cal.components([.Era, .Year, .Month, .Day], fromDate:NSDate())
    let today = cal.dateFromComponents(components)!

    components = cal.components([.Era, .Year, .Month, .Day], fromDate:self)
    let otherDate = cal.dateFromComponents(components)!

    return today.isEqualToDate(otherDate)
}

在 Swift 2.0 上为我工作

Answer 8

最佳答案的 Swift 版本：

let cal = NSCalendar.currentCalendar()
var components = cal.components([.Era, .Year, .Month, .Day], fromDate:NSDate())
let today = cal.dateFromComponents(components)!

components = cal.components([.Era, .Year, .Month, .Day], fromDate:aDate);
let otherDate = cal.dateFromComponents(components)!

if(today.isEqualToDate(otherDate)) {
    //do stuff
}

Answer 9

请参阅标题为“执行日历计算”的 Apple 文档条目 [链接]。

该页面上的清单 13 建议，要确定几天之间的午夜数，您可以使用：

- (NSInteger)midnightsFromDate:(NSDate *)startDate toDate:(NSDate *)endDate
{
    NSCalendar *calendar = [NSCalendar autoupdatingCurrentCalendar];
    NSInteger startDay = [calendar ordinalityOfUnit:NSDayCalendarUnit
                                             inUnit:NSEraCalendarUnit
                                            forDate:startDate];
    NSInteger endDay = [calendar ordinalityOfUnit:NSDayCalendarUnit
                                           inUnit:NSEraCalendarUnit
                                          forDate:endDate];
    return endDay - startDay;
}

然后，您可以使用该方法并查看它是否返回 0 来确定两天是否相同。

Answer 10

您还可以检查您的日期和当前日期之间的时间间隔：

[myDate timeIntervalSinceNow]

这将为您提供 myDate 和当前日期/时间之间的时间间隔（以秒为单位）。

链接。

编辑：请注意：我很清楚 [myDate timeIntervalSinceNow] 并不能明确确定 myDate 是否是今天。

我保留这个答案，这样如果有人正在寻找类似的东西并且 [myDate timeIntervalSinceNow] 有用，他们可能会在这里找到它。

Answer 11

基于最佳答案的 Swift 扩展：

extension NSDate {
    func isToday() -> Bool {
        let cal = NSCalendar.currentCalendar()
        if cal.respondsToSelector("isDateInToday:") {
            return cal.isDateInToday(self)
        }
        var components = cal.components((.CalendarUnitEra | .CalendarUnitYear | .CalendarUnitMonth | .CalendarUnitDay), fromDate:NSDate())
        let today = cal.dateFromComponents(components)!

        components = cal.components((.CalendarUnitEra | .CalendarUnitYear | .CalendarUnitMonth | .CalendarUnitDay), fromDate:self);
        let otherDate = cal.dateFromComponents(components)!
        return today.isEqualToDate(otherDate)
    }
}

Answer 12

如果您有很多这样的日期比较，那么对 calendar:components:fromDate 的调用就会开始占用大量时间。根据我所做的一些分析，它们似乎相当昂贵。

假设您正在尝试确定某个日期数组中的哪些日期（例如 NSArray *datesToCompare）与某个给定日期（例如 NSDate *baseDate）是同一天，那么您可以使用类似以下内容（部分改编自上面的答案）：

NSDate *baseDate = [NSDate date];

NSArray *datesToCompare = [NSArray arrayWithObjects:[NSDate date], 
                           [NSDate dateWithTimeIntervalSinceNow:100],
                           [NSDate dateWithTimeIntervalSinceNow:1000],
                           [NSDate dateWithTimeIntervalSinceNow:-10000],
                           [NSDate dateWithTimeIntervalSinceNow:100000],
                           [NSDate dateWithTimeIntervalSinceNow:1000000],
                           [NSDate dateWithTimeIntervalSinceNow:50],
                           nil];

// determine the NSDate for midnight of the base date:
NSCalendar* calendar = [NSCalendar currentCalendar];
NSDateComponents* comps = [calendar components:(NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit) 
                                       fromDate:baseDate];
NSDate* theMidnightHour = [calendar dateFromComponents:comps];

// set up a localized date formatter so we can see the answers are right!
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateStyle:NSDateFormatterMediumStyle];
[dateFormatter setTimeStyle:NSDateFormatterMediumStyle];

// determine which dates in an array are on the same day as the base date:
for (NSDate *date in datesToCompare) {
    NSTimeInterval interval = [date timeIntervalSinceDate:theMidnightHour];
    if (interval >= 0 && interval < 60*60*24) {
        NSLog(@"%@ is on the same day as %@", [dateFormatter stringFromDate:date], [dateFormatter stringFromDate:baseDate]);
    }
    else {
        NSLog(@"%@ is NOT on the same day as %@", [dateFormatter stringFromDate:date], [dateFormatter stringFromDate:baseDate]);
    }
}

输出：

Nov 23, 2011 1:32:00 PM is on the same day as Nov 23, 2011 1:32:00 PM
Nov 23, 2011 1:33:40 PM is on the same day as Nov 23, 2011 1:32:00 PM
Nov 23, 2011 1:48:40 PM is on the same day as Nov 23, 2011 1:32:00 PM
Nov 23, 2011 10:45:20 AM is on the same day as Nov 23, 2011 1:32:00 PM
Nov 24, 2011 5:18:40 PM is NOT on the same day as Nov 23, 2011 1:32:00 PM
Dec 5, 2011 3:18:40 AM is NOT on the same day as Nov 23, 2011 1:32:00 PM
Nov 23, 2011 1:32:50 PM is on the same day as Nov 23, 2011 1:32:00 PM

Answer 13

有一个比上述许多答案更简单的方法！

NSDate *date = ... // The date you wish to test
NSCalendar *calendar = [NSCalendar currentCalendar];

if([calendar isDateInToday:date]) {
    //do stuff
}

Answer 14

这可能会被重新设计为 NSDate 类别，但我使用了：（

// Seconds per day (24h * 60m * 60s)
#define kSecondsPerDay 86400.0f

+ (BOOL) dateIsToday:(NSDate*)dateToCheck
{
    // Split today into components
    NSCalendar* gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateComponents* comps = [gregorian components:(NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit|NSHourCalendarUnit|NSMinuteCalendarUnit|NSSecondCalendarUnit) 
                                        fromDate:[NSDate date]];

    // Set to this morning 00:00:00
    [comps setHour:0];
    [comps setMinute:0];
    [comps setSecond:0];
    NSDate* theMidnightHour = [gregorian dateFromComponents:comps];
    [gregorian release];

    // Get time difference (in seconds) between date and then
    NSTimeInterval diff = [dateToCheck timeIntervalSinceDate:theMidnightHour];
    return ( diff>=0.0f && diff<kSecondsPerDay );
}

但是，比较原始问题中的两个日期字符串几乎感觉“更干净”..）

Answer 15

对于 iOS7 及更早版本：

//this is now => need that for the current date
NSDate * now = [NSDate date];

NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
[calendar setTimeZone:[NSTimeZone systemTimeZone]];

NSDateComponents * components = [calendar components:( NSYearCalendarUnit|    NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit) fromDate: now];

[components setMinute:0];
[components setHour:0];
[components setSecond:0];

//this is Today's Midnight
NSDate *todaysMidnight = [calendar dateFromComponents: components];



//now timeIntervals since Midnight => in seconds
NSTimeInterval todayTimeInterval = [now timeIntervalSinceDate: todaysMidnight];

//now timeIntervals since OtherDate => in seconds
NSTimeInterval otherDateTimeInterval = [now timeIntervalSinceDate: otherDate];

if(otherDateTimeInterval > todayTimeInterval) //otherDate is not in today
{
    if((otherDateTimeInterval - todayTimeInterval) <= 86400) //86400 == a day total seconds
    {
        @"yesterday";
    }
    else
    {
        @"earlier";
    }
}
else
{
    @"today";
}


now = nil;
calendar = nil;
components = nil;
todaysMidnight = nil;

NSLog("Thank you :-)");

Answer 16

查看我们的 Erica Sadun 出色的 NSDate 扩展。使用起来非常简单。在这里进行修改：

http://github.com/erica/NSDate-Extensions

它已经在那里了在这篇文章中：https://stackoverflow.com/a/4052798/362310

Answer 17

正确且安全的解决方案，无需强制展开，适用于 Swift 2.2 和 iOS 8 之前的版本：

func isToday() -> Bool {
    let calendar = NSCalendar.currentCalendar()
    if #available(iOS 8.0, *) {
        return calendar.isDateInToday(self)
    }

    let todayComponents = calendar.components([.Era, .Year, .Month, .Day], fromDate:NSDate())
    let dayComponents = calendar.components([.Era, .Year, .Month, .Day], fromDate:self)

    guard let today = calendar.dateFromComponents(todayComponents),
        day = calendar.dateFromComponents(dayComponents) else {
        return false
    }

    return today.compare(day) == .OrderedSame
}

Answer 18

这是我的 2 美分答案，它建立在已接受的答案的基础上，但也支持更新的 API。注意：我使用公历，因为大多数时间戳都是 GMT，但可以根据需要更改您的时间戳

func isDateToday(date: NSDate) -> Bool {
    let calendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
    if calendar.respondsToSelector("isDateInToday:") {
        return calendar.isDateInToday(date)
    }
    let dateComponents = NSCalendarUnit.CalendarUnitYear | NSCalendarUnit.CalendarUnitMonth | NSCalendarUnit.CalendarUnitDay
    let today = calendar.dateFromComponents(calendar.components(dateComponents, fromDate: NSDate()))!
    let dateToCompare = calendar.dateFromComponents(calendar.components(dateComponents, fromDate: date))!

    return dateToCompare == today
}

Answer 19

我的解决方案是通过除法计算自 1970 年以来过去了多少天并比较整数部分

#define kOneDay (60*60*24)
- (BOOL)isToday {
  NSInteger offset = [[NSTimeZone defaultTimeZone] secondsFromGMT];

  NSInteger days =[self timeIntervalSince1970] + offset;
  NSInteger currentDays = [[NSDate date] timeIntervalSince1970] + offset;
  return (days / kOneDay == currentDays / kOneDay);
}

Answer 20

NSDate *dateOne = yourDate;
NSDate *dateTwo = [NSDate date];  

switch ([dateOne compare:dateTwo])
{  
    case NSOrderedAscending:  
        NSLog(@”NSOrderedAscending”);  
        break;  

    case NSOrderedSame: 
        NSLog(@”NSOrderedSame”);  
        break;

    case NSOrderedDescending:  
        NSLog(@”NSOrderedDescending”);  
        break;  
}