如何比较Objective-C中的两个日期

Question

我有两个日期:2009-05-11和当前日期.我想检查给定日期是否是当前日期.这怎么可能.

Answer 1

Cocoa有几种方法:

在NSDate

– isEqualToDate:  
– earlierDate:  
– laterDate:  
– compare:

当你使用时- (NSComparisonResult)compare:(NSDate *)anotherDate,你会回来其中一个:

The receiver and anotherDate are exactly equal to each other, NSOrderedSame
The receiver is later in time than anotherDate, NSOrderedDescending
The receiver is earlier in time than anotherDate, NSOrderedAscending.

例:

NSDate * now = [NSDate date];
NSDate * mile = [[NSDate alloc] initWithString:@"2001-03-24 10:45:32 +0600"];
NSComparisonResult result = [now compare:mile];

NSLog(@"%@", now);
NSLog(@"%@", mile);

switch (result)
{
    case NSOrderedAscending: NSLog(@"%@ is in future from %@", mile, now); break;
    case NSOrderedDescending: NSLog(@"%@ is in past from %@", mile, now); break;
    case NSOrderedSame: NSLog(@"%@ is the same as %@", mile, now); break;
    default: NSLog(@"erorr dates %@, %@", mile, now); break;
}

[mile release];

Answer 2

伙计.此功能将使您的日期与任何指定日期相匹配,并告知它们匹配与否的天气.您还可以修改组件以符合您的要求.

- (BOOL)isSameDay:(NSDate*)date1 otherDay:(NSDate*)date2 {
NSCalendar* calendar = [NSCalendar currentCalendar];

unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit;
NSDateComponents* comp1 = [calendar components:unitFlags fromDate:date1];
NSDateComponents* comp2 = [calendar components:unitFlags fromDate:date2];

return [comp1 day]   == [comp2 day] &&
[comp1 month] == [comp2 month] &&
[comp1 year]  == [comp2 year];}

此致,Naveed Butt

Answer 3

NSDate *today = [NSDate date]; // it will give you current date
NSDate *newDate = [NSDate dateWithString:@"xxxxxx"]; // your date 

NSComparisonResult result; 
//has three possible values: NSOrderedSame,NSOrderedDescending, NSOrderedAscending

result = [today compare:newDate]; // comparing two dates

if(result==NSOrderedAscending)
    NSLog(@"today is less");
else if(result==NSOrderedDescending)
    NSLog(@"newDate is less");
else
    NSLog(@"Both dates are same");

您可以使用其他方法来比较NSDate对象.在某些任务中,每种方法都会更有效.我选择了比较方法,因为它可以处理大多数基本日期比较需求.

Answer 4

此类别提供了一种比较NSDates的简洁方法:

#import <Foundation/Foundation.h>

@interface NSDate (Compare)

-(BOOL) isLaterThanOrEqualTo:(NSDate*)date;
-(BOOL) isEarlierThanOrEqualTo:(NSDate*)date;
-(BOOL) isLaterThan:(NSDate*)date;
-(BOOL) isEarlierThan:(NSDate*)date;
//- (BOOL)isEqualToDate:(NSDate *)date; already part of the NSDate API

@end

并实施:

#import "NSDate+Compare.h"

@implementation NSDate (Compare)

-(BOOL) isLaterThanOrEqualTo:(NSDate*)date {
    return !([self compare:date] == NSOrderedAscending);
}

-(BOOL) isEarlierThanOrEqualTo:(NSDate*)date {
    return !([self compare:date] == NSOrderedDescending);
}
-(BOOL) isLaterThan:(NSDate*)date {
    return ([self compare:date] == NSOrderedDescending);

}
-(BOOL) isEarlierThan:(NSDate*)date {
    return ([self compare:date] == NSOrderedAscending);
}

@end

使用简单:

if([aDateYouWantToCompare isEarlierThanOrEqualTo:[NSDate date]]) // [NSDate date] is now
{
    // do your thing ...
}

Answer 5

如果你把两个日期NSDate是你可以使用NSDate的compare:方法:

NSComparisonResult result = [Date2 compare:Date1];

if(result==NSOrderedAscending)
    NSLog(@"Date1 is in the future");
else if(result==NSOrderedDescending)
    NSLog(@"Date1 is in the past");
else
    NSLog(@"Both dates are the same");

您可以在这里查看文档.

Answer 6

通过这种方法,您还可以比较两个日期

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

if([dateOne compare:dateTwo] == NSOrderedAscending)
{

}

Answer 7

我找到的最好的方法是检查给定日期和今天之间的差异:

NSCalendar* calendar = [NSCalendar currentCalendar];
NSDate* now = [NSDate date];
int differenceInDays =
[calendar ordinalityOfUnit:NSCalendarUnitDay inUnit:NSCalendarUnitEra forDate:date] -
[calendar ordinalityOfUnit:NSCalendarUnitDay inUnit:NSCalendarUnitEra forDate:now];

根据Apple 日期和时间编程指南中的Calendrical Calculations清单13 [NSCalendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSEraCalendarUnit forDate:myDate]为您提供自该时代开始以来的午夜数.通过这种方式,可以轻松检查日期是昨天,今天还是明天.

switch (differenceInDays) {
    case -1:
        dayString = @"Yesterday";
        break;
    case 0:
        dayString = @"Today";
        break;
    case 1:
        dayString = @"Tomorrow";
        break;
    default: {
        NSDateFormatter* dayFormatter = [[NSDateFormatter alloc] init];
        [dayFormatter setLocale:usLocale];
        [dayFormatter setDateFormat:@"dd MMM"];
        dayString = [dayFormatter stringFromDate: date];
        break;
    }
}

Answer 8

NSDateFormatter *df= [[NSDateFormatter alloc] init];

[df setDateFormat:@"yyyy-MM-dd"];

NSDate *dt1 = [[NSDate alloc] init];

NSDate *dt2 = [[NSDate alloc] init];

dt1=[df dateFromString:@"2011-02-25"];

dt2=[df dateFromString:@"2011-03-25"];

NSComparisonResult result = [dt1 compare:dt2];

switch (result)
{

        case NSOrderedAscending: NSLog(@"%@ is greater than %@", dt2, dt1); break;

        case NSOrderedDescending: NSLog(@"%@ is less %@", dt2, dt1); break;

        case NSOrderedSame: NSLog(@"%@ is equal to %@", dt2, dt1); break;

        default: NSLog(@"erorr dates %@, %@", dt2, dt1); break;

}

享受编码......

Answer 9

你真正需要的是比较两个同类的对象。

1. 从字符串日期 (@"2009-05-11") 创建一个 NSDate ：
   http://blog.evandavey.com/2008/12/how-to-convert-a-string-to-nsdate.html

2. 如果当前日期也是字符串，则将其设为 NSDate。如果它已经是 NSDate，请保留它。