Format a date from a string

问题:

I'm trying to format a date from a string into another format.

For example: 2012-05-29 23:55:52 into 29/05 *newline* 2010.

I just don't get the logics behind NSDate and NSDateFormatter, I think..

Any help will be appreciated. Thanks :)

回答1:

You will need to create an NSDateFormatter, and then set it's dateFormat to match the first date you have, eg:

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

That will set your date formatter to recognise your date string. You can then obtain an NSDate object from this using

NSDate *myDate = [dateFormatter dateFromString:myDateString]; // myDateString is the 2012-05-29 23:55:52 string

This gives you a full NSDate object representing that date. Now you need to reformat the date and turn it back into a string, so set the dateFormat on your formatter to the new format, and get a new string representation of the returned date:

[dateFormatter setDateFormat:@"dd/MM\nyyyy"];
NSString *newlyFormattedDateString = [dateFormatter stringFromDate:myDate];
[dateFormatter release], dateFormatter = nil;

And voila! You have your new date :)

回答2:

If you're only doing simple string processing, Going through a date object is not really needed.

 let dateString = "2012-05-29 23:55:52"
 let dateParts = dateString.componentsSeparatedByCharactersInSet(NSCharacterSet(charactersInString: "- :")) 
 let newDateString = "\(dateParts[2])/\(dateParts[1])\n\(dateParts[0])"

 print(newDateString)

回答3:

Please find following code to convert date from one format to another format. It will give time in your current zone.

func convertDateFormat(sourceString : String, sourceFormat : String, destinationFormat : String) -> String{

    let dateFormatter = DateFormatter();
    dateFormatter.dateFormat = sourceFormat;

    if let date = dateFormatter.date(from: sourceString){
        dateFormatter.dateFormat = destinationFormat;
        return dateFormatter.string(from: date)
    }else{
        return ""
    }
}