Issues with stringWithFormat

问题

Please how do I make my stringWithFormat/initWithFormat to display am/pm instead of 24hrs, even though users selects am/pm from the pickerviewer? When a user select time; eg 4:15 pm, instead of it to display 4:15pm as confirmation, it displays 16:15 instead. I want it as 4:15pm. PLEASE HELP!!

-(IBAction)datePickerValueChanged:(id)sender
{ NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"]];
[dateFormatter setDateFormat:@"h:mm:ss a"];
NSString *strDate = [dateFormatter stringFromDate:self.pick.date];

dateArray = [strDate componentsSeparatedByString:@":"];

NSDate *current = [NSDate date];
NSString *currentTime = [dateFormatter stringFromDate:current];
NSArray *currArray = [currentTime componentsSeparatedByString:@":"];

curr = [currArray[0] intValue]*60 + [currArray[1] intValue];
min = [currArray[0] intValue]*60 + [currArray[1] intValue] + 30;
next = [[dateArray objectAtIndex:0] intValue]*60 +[[dateArray objectAtIndex:1] intValue];

....This is where values are displayed:

             NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
             [dateFormatter setDateFormat:@"yyyy-MM-dd"];
             NSString *strDate = [dateFormatter stringFromDate:[NSDate date]];

             time = [[NSString alloc]initWithFormat:@"%@T%@:%@:00",strDate, [dateArray objectAtIndex:0], [dateArray objectAtIndex:1]];
             NSString *msg = [[NSString alloc] initWithFormat:@"%@ %@ %@ %@ ?", NSLocalizedString(@"do_ticket", nil), self.category.description,NSLocalizedString(@"at", nil),[[NSString alloc]initWithFormat:@"%@:%@", [dateArray objectAtIndex:0], [dateArray objectAtIndex:1]]];
             alert_tick = [[UIAlertView alloc] initWithTitle:nil
                                                     message:msg
                                                    delegate:self
                                           cancelButtonTitle:nil
                                           otherButtonTitles:NSLocalizedString(@"Yes", nil), NSLocalizedString(@"No", nil), nil];
             [alert_tick show];
}

回答1:

Use NSDateFormatter. It doesn't matter that server values are given in 24h format, because your date formatting string can accommodate that (i.e. instead of using "h" for hours when calling setDateFormat:, which represents am/pm format, use "H" for 24h format).

回答2:

Use the format @"hh:mm a" instead.

Example:

NSDate *today = [NSDate dateWithTimeIntervalSinceNow:0];
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"hh:mm a"];
NSDate *formattedDate = [formatter stringFromDate:today];
NSLog(@"date : %@", formattedDate);

Output:

date : 09:58 AM

来源：https://stackoverflow.com/questions/24914761/issues-with-stringwithformat