如何确定今天是否有NSDate？

如何检查NSDate今天是否属于？

我曾经使用中的前10个字符来检查它[aDate description]。[[aDate description] substringToIndex:10]返回类似"YYYY-MM-DD"的字符串，所以我将字符串与所返回的字符串进行了比较[[[NSDate date] description] substringToIndex:10]。

有没有更快速和/或更整洁的检查方法？

谢谢。

在macOS 10.9+和iOS 8+中，NSCalendar / Calendar上有一种方法可以做到这一点！

- (BOOL)isDateInToday:(NSDate *)date 

所以你只要做

目标C：

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

斯威夫特3：

let today = Calendar.current.isDateInToday(date)

您可以比较日期成分：

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语句更简洁，更易理解：

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，我已经采纳了你的建议。我必须查询一下什么时代，因此对于任何其他不知道的人，它可以区分BC和AD。对于大多数人来说，这可能是不必要的，但是它很容易检查并增加了确定性，因此我将其包括在内。如果您追求速度，那么这可能不是一个好方法。

注意，与SO上的许多答案一样，在7年后，这已经完全过时了。在Swift中，只需使用.isDateInToday

这是您问题的分支，但是如果您要使用“今天”或“昨天”来打印NSDate，请使用该功能

- (void)setDoesRelativeDateFormatting:(BOOL)b

对于NSDateFormatter

我将尝试将今天的日期归一化为午夜，将第二个日期归一化，归一化为午夜，然后比较是否是相同的NSDate。

在Apple的示例中，这是如何规范化到今天的午夜日期，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];

由Catfish_Man建议的工作Swift 3和4扩展：

extension Date {

    func isToday() -> Bool {
        return Calendar.current.isDateInToday(self)
    }

}

无需费心处理组件，时代和事物。

NSCalendar提供了一种获取现有日期的特定时间单位的开始的方法。

该代码将获取今天的开始日期和另一个日期并将其进行比较。如果计算结果为NSOrderedSame，则两个日期都在同一天-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
}

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

Swift版本的最佳答案：

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
}

请参阅Apple文档标题为“执行日历计算”的文档条目[link]。

该页面上的清单13建议使用以下方法确定两天之间的午夜数：

- (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，您可以使用该方法确定两天是否相同，并查看它是否返回0。

您还可以检查您拥有的日期与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：所有人注意：我很清楚[myDate timeIntervalSinceNow]不会明确确定myDate是否是今天。

我将原样保留此答案，以便如果某人正在寻找相似的东西并且[myDate timeIntervalSinceNow]有用，他们可能会在这里找到。

Swift扩展基于最佳答案：

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)
    }
}

如果您有很多这样的日期比较，则calendar:components:fromDate开始通话会占用大量时间。根据我所做的一些分析，它们似乎非常昂贵。

假设您要尝试从某个日期数组（例如）确定哪个日期NSArray *datesToCompare与给定日期（例如）的同一天NSDate *baseDate，那么您可以使用类似以下内容的方法（部分改编自上述答案）：

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

有比上述答案更简单的方法！

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

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

这可能可以作为NSDate类别重做，但是我使用了：

// 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，像原始问题中那样比较两个日期字符串几乎感觉“更干净”。）

对于iOS7和更早版本：

//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 :-)");

查看我们的Erica Sadun的出色表现NSDate extension。使用非常简单。在这里精细：

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

它已经在这篇文章中了：https : //stackoverflow.com/a/4052798/362310

在Swift 2.2以及iOS 8之前的版本中，无需强制解开的正确，安全的解决方案：

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
}

这是我的2美分答案，基于公认的答案，但也支持较新的API。注意：由于大多数时间戳都是格林尼治标准时间，因此我使用公历，但请根据自己的喜好更改日历

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
}

我的解决方案是按除法计算自1970年以来经过了多少天，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);
}

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;  
}