How do I format the current date for the user'

问题:

I have this code where I'm trying to get the current date and format it in the current locale.

NSDate *now = [NSDate date];  //  gets current date
NSString *sNow = [[NSString alloc] initWithFormat:@"%@",now];
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"mm-dd-yyyy"];
insertCmd = [insertCmd stringByAppendingString: formatter setDateFormat: @"MM.dd.yyyy"];

I know the last line is wrong, but can't seem to figure it out... "insertCmd" is a NSString that I'm building for a FMDB command.

Help would be greatly appreciated, or a pointer to the "doc" where it's described.

回答1:

I wouldn't use setDateFormat in this case, because it restricts the date formatter to a specific date format (doh!) - you want a dynamic format depending on the user's locale.

NSDateFormatter provides you with a set of built-in date/time styles that you can choose from, i.e. NSDateFormatterMediumStyle, NSDateFormatterShortStyle and so on.

So what you should do is:

NSDate* now = [NSDate date];
NSDateFormatter* df = [[NSDateFormatter alloc] init];
[df setDateStyle:NSDateFormatterMediumStyle];
[df setTimeStyle:NSDateFormatterShortStyle];
NSString* myString = [df stringFromDate:now];

This will provide you with a string with a medium-length date and a short-length time, all depending on the user's locale. Experiment with the settings and choose whichever you like.

Here's a list of available styles: https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSDateFormatter_Class/Reference/Reference.html#//apple_ref/c/tdef/NSDateFormatterStyle

回答2:

In addition to jiayow answer you can specify your custom 'template' to get localized version:

+ (NSString *)formattedDate:(NSDate *)date usingTemplate:(NSString *)template {
    NSDateFormatter* formatter = [NSDateFormatter new];

    formatter.dateFormat = [NSDateFormatter dateFormatFromTemplate:template options:0 locale:formatter.locale];

    return [formatter stringFromDate:date];
}

Example usage for US/DE locale:

NSLocale *enLocale = [NSLocale localeWithLocaleIdentifier:@"en_US"];
NSLocale *deLocale = [NSLocale localeWithLocaleIdentifier:@"de"];

// en_US:   MMM dd, yyyy
formatter.dateFormat = [NSDateFormatter dateFormatFromTemplate:@"ddMMMyyyy" options:0 locale:enLocale];
// de:      dd. MMM yyyy
formatter.dateFormat = [NSDateFormatter dateFormatFromTemplate:@"ddMMMyyyy" options:0 locale:deLocale];

// en_US:   MM/dd/yyyy
formatter.dateFormat = [NSDateFormatter dateFormatFromTemplate:@"ddyyyyMM" options:0 locale:enLocale];
// de:      dd.MM.yyyy
formatter.dateFormat = [NSDateFormatter dateFormatFromTemplate:@"ddyyyyMM" options:0 locale:deLocale];

// en_US    MM/dd
formatter.dateFormat = [NSDateFormatter dateFormatFromTemplate:@"MMdd" options:0 locale:enLocale];
// de:      dd.MM.
formatter.dateFormat = [NSDateFormatter dateFormatFromTemplate:@"MMdd" options:0 locale:deLocale];

回答3:

Here's a Swift 5 version of @JiaYou's answer:

func format(date: Date) -> String {
    let formatter = DateFormatter()
    formatter.dateStyle = .medium
    formatter.timeStyle = .none
    return formatter.string(from: date)
}

Here I need date only, so I indicate the timeStyle as none.

回答4:

If you want the localized date and time this will give it to you:

    NSString *localizedDateTime = [NSDateFormatter localizedStringFromDate:[NSDate date] dateStyle:NSDateFormatterShortStyle timeStyle:NSDateFormatterShortStyle];

The code above does not give you the localized date and time.