iOS：比较两个没有时间部分的 NSDate-s

iOS: Compare two NSDate-s without time portion

提问by cyclingIsBetter

I want to compare two dates: date1 and date2

我想比较两个日期：date1 和 date2

2011-06-06 12:59:48.994 Project[419:707] firstDate:2011-06-06 10:59:21 +0000
2011-06-06 12:59:49.004 Project[419:707] selectedData:2011-06-06 10:59:17 +0000

but these dates have different time and when I use NSOrderedSame it don't work fine, how can I solve?

但是这些日期有不同的时间，当我使用 NSOrderedSame 时它不能正常工作，我该如何解决？

my code:

我的代码：

NSDate *firstDate = [[appDelegate.project objectAtIndex:i]objectAtIndex:3];
NSDate *secondDate = [[appDelegate.project objectAtIndex:i]objectAtIndex:4];

NSCalendar *calendar = [NSCalendar currentCalendar];
NSInteger comps = (NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit);

NSDateComponents *date1Components = [calendar components:comps 
                                                            fromDate:firstDate];
NSDateComponents *date2Components = [calendar components:comps 
                                                            fromDate:secondDate];
NSDateComponents *date3Components = [calendar components:comps fromDate:appDelegate.selectedDate];

NSLog(@"firstDate:%@", [date1Components date]);
NSLog(@"secondDate:%@", [date2Components date]);
NSLog(@"selectedData:%@", [date3Components date]);

NSComparisonResult compareStart = [[date1Components date] compare: [date3Components date]]; 
NSComparisonResult compareEnd = [[date2Components date] compare: [date3Components date]]; 

if ((compareStart == NSOrderedAscending || compareStart == NSOrderedSame)
     && (compareEnd == NSOrderedDescending || compareEnd == NSOrderedSame))

{
    NSLog(@"inside");

Then I want to compare my dates and entry inside the "if" when date1 <= selectedDate <= date2; now I understand because I have a warning: I should add this "[date1Components date]" and it work; the problem is that I have in the NSLog null values, why??

然后我想在 date1 <= selectedDate <= date2; 时比较我的日期和“if”中的条目。现在我明白了，因为我有一个警告：我应该添加这个“[date1Components date]”并且它可以工作；问题是我在 NSLog 中有空值，为什么？

回答by vikingosegundo

NSCalendar *calendar = [NSCalendar currentCalendar];
NSInteger comps = (NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear);

NSDateComponents *date1Components = [calendar components:comps 
                                                fromDate: date1];
NSDateComponents *date2Components = [calendar components:comps 
                                                fromDate: date2];

date1 = [calendar dateFromComponents:date1Components];
date2 = [calendar dateFromComponents:date2Components];

NSComparisonResult result = [date1 compare:date2];
if (result == NSOrderedAscending) {
} else if (result == NSOrderedDescending) {
}  else {
    //the same
}

---

---

There is another handy method to create for a given date the date that represents the start of a given unit: [aCalendar rangeOfUnit:startDate:interval:forDate:]
To illustrate how this method works, see this code, that easily creates the date for the beginning of the day, week, month and year for a given date (here: now).

还有另一种方便的方法可以为给定日期创建表示给定单位开始的日期： 为了说明此方法的工作原理，请参阅此代码，它可以轻松创建日、周、月和年的开始日期对于给定日期（此处：现在）。[aCalendar rangeOfUnit:startDate:interval:forDate:]

NSDate *now = [NSDate date];
NSDate *startOfToday = nil;
NSDate *startOfThisWeek = nil;
NSDate *startOfThisMonth = nil;
NSDate *startOfThisYear = nil;
[[NSCalendar currentCalendar] rangeOfUnit:NSDayCalendarUnit startDate:&startOfToday interval:NULL forDate:now];
[[NSCalendar currentCalendar] rangeOfUnit:NSWeekCalendarUnit startDate:&startOfThisWeek interval:NULL forDate:now];
[[NSCalendar currentCalendar] rangeOfUnit:NSMonthCalendarUnit startDate:&startOfThisMonth interval:NULL forDate:now];
[[NSCalendar currentCalendar] rangeOfUnit:NSYearCalendarUnit startDate:&startOfThisYear interval:NULL forDate:now];

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateStyle:NSDateFormatterFullStyle];
[formatter setTimeStyle:NSDateFormatterFullStyle];

NSLog(@"%@", [formatter stringFromDate:now]);
NSLog(@"%@", [formatter stringFromDate:startOfToday]);
NSLog(@"%@", [formatter stringFromDate:startOfThisWeek]);
NSLog(@"%@", [formatter stringFromDate:startOfThisMonth]);
NSLog(@"%@", [formatter stringFromDate:startOfThisYear]);

result:

结果：

Thursday, July 12, 2012, 4:36:07 PM Central European Summer Time 
Thursday, July 12, 2012, 12:00:00 AM Central European Summer Time 
Sunday, July 8, 2012, 12:00:00 AM Central European Summer Time 
Sunday, July 1, 2012, 12:00:00 AM Central European Summer Time 
Sunday, January 1, 2012, 12:00:00 AM Central European Standard Time

this allows us to shorten the first code to:

这允许我们将第一个代码缩短为：

[[NSCalendar currentCalendar] rangeOfUnit:NSDayCalendarUnit startDate:&date1 interval:NULL forDate:date1];
[[NSCalendar currentCalendar] rangeOfUnit:NSDayCalendarUnit startDate:&date2 interval:NULL forDate:date2];

NSComparisonResult result = [date1 compare:date2];
if (result == NSOrderedAscending) {
} else if (result == NSOrderedDescending) {
}  else {
    //the same
}

Note, that in this code, date1and date2will be overwritten. Alternatively you can pass in a reference to another NSDate pointer for startDateas shown in the code above, where nowstays untouched.

注意，在这段代码中，date1和date2将被覆盖。或者，您可以传递对另一个 NSDate 指针的引用，startDate如上面的代码所示，其中now保持不变。

回答by Exsigth

I have used another method with NSDateFormatter and a string comparison, less smarter than NSDate comparemethod but faster to write and flexible enough to do variety of comparison :

我在 NSDateFormatter 和字符串比较中使用了另一种方法，它不如 NSDate比较方法聪明，但编写速度更快，并且足够灵活，可以进行各种比较：

NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:@"yyyy-MM-dd"];

if ([[dateFormat stringFromDate:date1] isEqualToString:[dateFormat stringFromDate:date2]])
{
    //It's the same day
}

回答by Paul Patterson

Okay, so it's a few years after the original question was asked, but it's probably worth mentioning that NSCalendarnow has a number of methods that make certain date comparison questions much more straight-forward:

好的，所以在最初的问题被问到几年之后，但可能值得一提的是，NSCalendar现在有许多方法可以使某些日期比较问题更加直接：

NSCalendar *currentCalendar = [NSCalendar currentCalendar];
Bool sameDay = [currentCalendar isDate:dateA inSameDayAsDate:dateB];

回答by LuAndre

Swift Version, Comparing Dates and ignoring their time.

Swift 版本，比较日期并忽略它们的时间。

let dateExam1:NSDate = NSDate.init(timeIntervalSinceNow: 300)
let dateExam2:NSDate = NSDate.init(timeIntervalSinceNow: 10000)

let currCalendar = NSCalendar.currentCalendar()

let dateCompanent1:NSDateComponents = currCalendar.components([.Year,.Month,.Day], fromDate: dateExam1)
let dateCompanent2:NSDateComponents = currCalendar.components([.Year,.Month,.Day], fromDate: dateExam2)

let date1WithoutTime:NSDate? = currCalendar .dateFromComponents(dateCompanent1)
let date2WithoutTime:NSDate? = currCalendar .dateFromComponents(dateCompanent2)
if (date1WithoutTime != nil) && (date2WithoutTime != nil)
{
    let dateCompResult:NSComparisonResult = date1WithoutTime!.compare(date2WithoutTime!)
    if (dateCompResult == NSComparisonResult.OrderedSame)
    {
        print("Same Dates")
    }
    else
    {
        print("Different Dates")
    }
}