NSDate 的转换真的很奇怪

发布于 2024-11-14 16:25:37 字数 305 浏览 4 评论 0原文

我有一个时间：7:46 am

我想将其转换为 NSDate。我这样做：

NSDateFormatter *f = [NSDateFormatter new];
[f setDateFormat:@"h:mm a"];
NSDate *sr = [f dateFromString:@"7:46 am"];

我 NSLog sr 并得到 1969-12-31 22:46:00 +0000

这些时间不一样。为什么这么乱？

原文

I have a time: 7:46 am

I want to convert this to NSDate. I do this:

NSDateFormatter *f = [NSDateFormatter new];
[f setDateFormat:@"h:mm a"];
NSDate *sr = [f dateFromString:@"7:46 am"];

I NSLog sr and I get 1969-12-31 22:46:00 +0000

Those times are not the same. Why is this so messed up?

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甚是思念 2024-11-21 16:25:37

没有。这并不奇怪。 NSDateConverter & NSDate 只是在这里完成他们的预期工作。

您正在尝试将 "7:46 am" 转换为日期。它仅包含时间。字符串中未指定日期。如果未指定日期，NSDate 将默认为 "1970-01-01"（Unix 纪元）。因此，转换字符串后，您将获得日期“1970-01-01 7:46 am”。当您尝试在 NSLog 中显示此内容时，如果会在调整时区偏移值后显示日期。我猜你住在日本或韩国。您所在区域的偏移量可能是+09:00。因此它显示减去偏移量的日期。因此您会在日志中看到 "1969-12-31 22:46:00 +0000"。

您可以使用以下方法将该时间设置为特定日期，可以是今天。

NSString *timeStr = @"7:46 am";
NSDateFormatter *f = [NSDateFormatter new];
[f setDateFormat:@"yyyy-MM-dd"];
NSString *dateStr = [f stringFromDate:[NSDate date]]; // dateStr = 2011-06-10
dateStr = [dateStr stringByAppendingFormat:@" %@", timeStr]; // dateStr = 2011-06-10 7:46 am 
[f setDateFormat:@"yyyy-MM-dd h:mm a"];
NSDate *sr = [f dateFromString:dateStr];

No. Its not strange. NSDateConverter & NSDate are just doing their intended job here.

You are trying to convert "7:46 am" into a date. It contains only the time. No date is specified in the string. NSDate will default to "1970-01-01"(Unix epoch) if no date is specified. So after you convert the string you will get the date "1970-01-01 7:46 am". When you trying to display this in NSLog, if will display the date after adjusting the timeZone offset value. I guess you live in Japan or Korea. Probably the offset of your region is +09:00. So it diaplays the date subtracting the offset. So you are seeing "1969-12-31 22:46:00 +0000" in the log.

You can use the following method to set that time to a particular date, may be today.

NSString *timeStr = @"7:46 am";
NSDateFormatter *f = [NSDateFormatter new];
[f setDateFormat:@"yyyy-MM-dd"];
NSString *dateStr = [f stringFromDate:[NSDate date]]; // dateStr = 2011-06-10
dateStr = [dateStr stringByAppendingFormat:@" %@", timeStr]; // dateStr = 2011-06-10 7:46 am 
[f setDateFormat:@"yyyy-MM-dd h:mm a"];
NSDate *sr = [f dateFromString:dateStr];

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拥醉 2024-11-21 16:25:37

您没有提供日期或时区...假设您想表达“今天上午 7:42”，您可以使用以下代码：

NSDate *currentDate = [NSDate date];
NSDateComponents *comps = [[NSDateComponents alloc] init];
[comps setHour:7];
[comps setMinute:42];
NSDate *myDate = [calendar dateByAddingComponents:comps toDate:currentDate options:0];
[comps release];

myDate 的 NSLog 现在应该为您提供预期的输出（假设您想要 Today@7 :46am）。

You aren't providing the day or the timezone... assuming you want to express "today at 7:42am", you can use this code:

NSDate *currentDate = [NSDate date];
NSDateComponents *comps = [[NSDateComponents alloc] init];
[comps setHour:7];
[comps setMinute:42];
NSDate *myDate = [calendar dateByAddingComponents:comps toDate:currentDate options:0];
[comps release];

The NSLog of myDate should give you the expected output now (assuming you wanted today@7:46am).

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