如何在 Objective-C 中比较两个日期

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

Cocoa 有几种方法可以做到这一点:

在 NSD 日期

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

当你使用- (NSComparisonResult)compare:(NSDate *)anotherDate，你会得到以下其中之一：

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.

example:

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];