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我对 NSDate 比较有疑问。我在谷歌搜索我的问题时尝试了几种解决方案，但没有任何改变：我比较两个日期，我总是得到 NSOrderedSame 或 NSTimeIntervals = 0.0000; 之间的差异；

我的代码如下所示：

NSDateFormatter *inputFormatter = [[NSDateFormatter alloc] init];
    [inputFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];

    for (checklisteModel *updateRecord in updateArray) 
    {

        NSDate *serverDate = [inputFormatter dateFromString:updateRecord.last_update];

        NSString *lastUpdateFromLocalRecord = [self getLastUpdateForChecklisteItemWithID:updateRecord.checklisteID];
        NSDate *localDate = [inputFormatter dateFromString:lastUpdateFromLocalRecord];

        NSDateFormatter* fmt = [[NSDateFormatter alloc] init];
        NSLog(@"checkliste ID: %i",updateRecord.checklisteID);
        NSLog(@"server Date: ----- %@",[fmt stringFromDate:serverDate]);
        NSLog(@"local Date: ----- %@",lastUpdateFromLocalRecord);



        NSLog(@"difference of dates: %f",[serverDate timeIntervalSinceDate:localDate]);


        NSTimeInterval distanceBetweenDates = [serverDate timeIntervalSinceDate:localDate];
        double secondsInMinute = 60;
        NSInteger secondsBetweenDates = distanceBetweenDates / secondsInMinute;

        if (secondsBetweenDates == 0)
            NSLog(@"seconds between == 0");
        else if (secondsBetweenDates < 0)
            NSLog(@"seconds between < 0");
        else
            NSLog(@"seconds between > 0");



        //last_update on server is earlier than local
        if ([serverDate compare:localDate] == NSOrderedAscending) 
        {

            NSLog(@"Server data is earlier than local data");
            NSLog([NSString stringWithFormat:@"server data: %@, local data: %@",updateRecord.last_update,lastUpdateFromLocalRecord]);
        }
        // server data is later than local data
        else if ([serverDate compare:localDate] == NSOrderedDescending) 
        {

            NSLog(@"Server data is later than local data");
            NSLog([NSString stringWithFormat:@"server data: %@, local data: %@",updateRecord.last_update,lastUpdateFromLocalRecord]);
        }
        else 
        {
            NSLog(@"Server data and local data are the same");
        }
    }

我的部分调试显示了这一点：

checkliste ID: 21
server Date: ----- 
local Date: ----- 2012-10-29 10:13:46
difference of dates: 3810.000000
seconds between > 0
Server data is later than local data
server data: 2012-10-29 11:17:16, local data: 2012-10-29 10:13:46
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1 回答 1

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NSLog(@"server Date: ----- %@",updateRecord.last_update);

你没有serverDate在这里登录，所以正如 Hot Licks 建议的那样，它很有可能是零。你可以nil在 Objective-C 中发送消息，结果是0or nil。你认为 NSOrderedSame 的价值是什么？我敢赌一美元0。

[inputFormatter setDateFormat:@"yyyy-MM-dd HH:mm"];

我注意到您的日期格式化程序的输入格式与您正在记录的内容不完全匹配，因此预期输入与您提供的内容之间的差异可能足以阻止格式化程序创建日期。尝试将秒数添加到inputFormatter.

于 2012-10-29T12:48:07.213 回答