如何格式化字符串变量中的数据 [英] How to format data from string variable

问题描述

我有一个保留日期的NSString:

I have a NSString that keeps date:

1900-01-01T11:00:00

我需要对其进行格式化，所以我有一个格式化程序:

I need to format it, so I have a formatter:

NSDateFormatter *df = [[NSDateFormatter alloc] init];
    [df setDateFormat:@"dd/MM/yyyy hh:mm:ss a"];

如何立即设置此字符串的格式?

How to format this string now?

NSString* formatedDateString = [df ???];

推荐答案

创建日期格式化程序，该日期格式化程序返回给定字符串的日期对象，创建第二个日期格式化程序，从该日期返回所需格式的字符串

Create a date formatter, that returns a date object for for the given string, create a second date formatter, that returns a string in the desired format from that date.

NSDateformatter *inputFormatter = [[NSDateformatter alloc] init];
[inputFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss"];  
[inputFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"]];
NSDate *date = [inputFormatter dateFromString:dateString];

NSDateformatter *outputFormatter = [[NSDateformatter alloc] init];
[outputFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"]];
[outputFormatter setDateFormat:@"dd/MM/yyyy hh:mm:ss a"];  

NSString *outputString = [outputFormatter stringFromDate:date];

---

但是您也可以让输出日期格式化程序根据地区来决定样式:

---

But you could also let the output date formatter decide the style in respect to the locale:

NSDateformatter *outputFormatter = [[NSDateformatter alloc] init];
[outputFormatter setDateStyle:NSDateFormatterShortStyle];  
[outputFormatter setTimeStyle:NSDateFormatterShortStyle]; 
NSString *outputString = [outputFormatter stringFromDate:date];

对于美国语言环境，您现在应该选择所需的格式.

for a american locale, you should now cat the desired format.

如果要为用户强制使用格式"dd/MM/yyyy hh:mm:ss a"，则还应设置输出日期格式程序的区域设置.

if you want to enforce format "dd/MM/yyyy hh:mm:ss a" for the user, you should also set the locale of the output date formatter.

完整的命令行示例.

int main(int argc, const char * argv[])
{

    @autoreleasepool {


        NSString *dateString1 = @"2012-12-31T11:00:00";
        NSString *dateString2 = @"2012-12-31T14:00:00";
        NSDateFormatter *inputFormatter = [[NSDateFormatter alloc] init];
        [inputFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"]];
        [inputFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss"];

        NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];
        [outputFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"]];
        [outputFormatter setDateFormat:@"dd/MM/yyyy hh:mm:ss a"];


        NSDate *date1 = [inputFormatter dateFromString:dateString1];
        NSDate *date2 = [inputFormatter dateFromString:dateString2];

        NSString *outputString1 = [outputFormatter stringFromDate:date1];
        NSString *outputString2 = [outputFormatter stringFromDate:date2];

        NSLog(@"%@", outputString1);
        NSLog(@"%@", outputString2);

    }
    return 0;
}

如果您不像那样设置语言环境，请执行以下操作:它不是碰巧是"en_US"

If you dont set the locale like [outputFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"]]; it will lead do a ugly mix of formats with user's sefault locale, if it not happend to be 'en_US'

即德语: 2012年12月31日02:00:00 nachm.这是德语中未使用的格式.

ie in German: 31/12/2012 02:00:00 nachm. This is a format not used in german.

要支持用户的语言和语言环境，您应该改用其他样式.

To support user's language and locale you should instead use the different styles.

提供的 q&a rmaddy表示，在极少数情况下，解析格式会被重写.为避免这种情况，请将输入格式的格式设置为特定的语言环境，例如 [inputFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"]];

The q&a rmaddy provided indicates, that there are rare cases, where the parse format gets rewritten. To avoid this, set the input formatted's format to a certain locale, like [inputFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"]];

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