如何以编程方式获取 NSDate plist 表示形式？

发布于 2024-10-29 02:21:01 字数 1014 浏览 6 评论 0原文

由于plist是xml，即文本，因此当将NSDate对象写入plist时，结果是这样的：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
      <date>2011-04-01T02:09:15Z</date>
</plist>

我想获取该字符串（011-04-01T02:09:15Z ）直接，没有所有周围环境。必须有一种更明智的方法来做到这一点：

NSString *xmlRepresentationOfCurrentDate = [[[[[[[NSString alloc] initWithData:[NSPropertyListSerialization dataFromPropertyList:self format:kCFPropertyListXMLFormat_v1_0 options:0 error:NULL] encoding:NSUTF8StringEncoding] autorelease] componentsSeparatedByString:@"<date>"] objectAtIndex:1] componentsSeparatedByString:@"</date>"] objectAtIndex:0];

使事情变得复杂的是上面的表示是 GMT，并且显然时区是在创建 NSDate 对象期间设置的。我看到的上述代码的替代方法是获取 GMT 偏移量，在 dateWithTimeInterval:sinceDate: 方法中使用它来获取 GMT 日期，然后使用 NSDateFormatter 来获取 GMT 日期。写出上面的字符串。然而，因为这会带来更多的开销。

有什么办法可以只获取该 xml 字符串吗？

原文

Since plist is xml, which is text, when an NSDate object is written into a plist, the result is something like this:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
      <date>2011-04-01T02:09:15Z</date>
</plist>

I would like to obtain that string (011-04-01T02:09:15Z) directly, without all the surroundings. There has to be a more sensible way to do it than:

NSString *xmlRepresentationOfCurrentDate = [[[[[[[NSString alloc] initWithData:[NSPropertyListSerialization dataFromPropertyList:self format:kCFPropertyListXMLFormat_v1_0 options:0 error:NULL] encoding:NSUTF8StringEncoding] autorelease] componentsSeparatedByString:@"<date>"] objectAtIndex:1] componentsSeparatedByString:@"</date>"] objectAtIndex:0];

What complicates it is the fact that the representation above is GMT, and apparently the timezone is set during the creation of the NSDate object. An alternative to the above code I see is to get the GMT offset, use it in the dateWithTimeInterval:sinceDate: method to get the GMT date, and then use the NSDateFormatter to write out the above string. However, since that has even more overhead.

Is there any way to get just that xml string?

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迎风吟唱 2024-11-05 02:21:01

如果您确实要创建仅包含单个日期的属性列表，那么您发布的代码似乎是正确的方法。我可以理解您可能会觉得这有点麻烦，但您始终可以将其粘贴到 NSDate 上的类别中的方法中，以便您可以直接从属性列表格式读取或写入日期。

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小忆控 2024-11-05 02:21:01

NSDate 的 description 方法返回一个使用 YYYY-MM-DD HH:MM:SS ±HHMM 格式的字符串。

编辑：executor21指出以下部分仅适用于OS X，不适用于iOS。

如果您不想要该格式，可以使用 descriptionWithCalendarFormat:timeZone:locale: 代替并定义您自己的格式。请参阅

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七度光 2024-11-05 02:21:01

考虑到这种情况，NSDateFormatter 实际上是最好的选择——我需要在 iOS 3.1.3 及更高版本的设备上运行它，所以 dataWithPropertyList:format:options:error: 方法（在4.0) 不是一个选项，而
dataFromPropertyList:format:errorDescription: 预计将被弃用。

另外，我在上面犯了一个错误：它应该是

NSString *xmlRepresentationOfCurrentDate = [[[[[[[NSString alloc] initWithData:[NSPropertyListSerialization dataWithPropertyList:self format:kCFPropertyListXMLFormat_v1_0 options:0 error:NULL] encoding:NSUTF8StringEncoding] autorelease] componentsSeparatedByString:@"<date>"] objectAtIndex:1] componentsSeparatedByString:@"</date>"] objectAtIndex:0];

但实际的全版本解决方案是 NSDate 上的类别方法：

-(NSString *)xmlRepresentation{
    NSDateFormatter *formatter = [[[NSDateFormatter alloc] init] autorelease];
    [formatter setTimeStyle:NSDateFormatterFullStyle];

    [formatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss"];
    [formatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];

    return [[formatter stringFromDate:self] stringByAppendingString:@"Z"];
}

It seems like the NSDateFormatter is actually the best option given the circumstances -- I need to run this on devices with iOS 3.1.3 and above, so dataWithPropertyList:format:options:error: method (introduced in 4.0) isn't an option, while
dataFromPropertyList:format:errorDescription: is slated for deprecation.

Also, I made a mistake above: it should be

NSString *xmlRepresentationOfCurrentDate = [[[[[[[NSString alloc] initWithData:[NSPropertyListSerialization dataWithPropertyList:self format:kCFPropertyListXMLFormat_v1_0 options:0 error:NULL] encoding:NSUTF8StringEncoding] autorelease] componentsSeparatedByString:@"<date>"] objectAtIndex:1] componentsSeparatedByString:@"</date>"] objectAtIndex:0];

But the actual, all-versions solution is a category method on NSDate:

-(NSString *)xmlRepresentation{
    NSDateFormatter *formatter = [[[NSDateFormatter alloc] init] autorelease];
    [formatter setTimeStyle:NSDateFormatterFullStyle];

    [formatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss"];
    [formatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];

    return [[formatter stringFromDate:self] stringByAppendingString:@"Z"];
}

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