How to parse a date string into an NSDate object in iOS?

问题

I am trying to parse a date string from xml into an NSDate object in an iPhone app

I am aware this must have been asked before, however, I believe I have the right syntax, but it is not working. Is there a problem with my code?

The date string I need to parse is:

2011-01-21T12:26:47-05:00

The code I am using to parse it is:

self.dateFormatter = [[NSDateFormatter alloc] init];
    [self.dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
    [self.dateFormatter setLocale:[[[NSLocale alloc] initWithLocaleIdentifier:@\"en_US_POSIX\"] autorelease]];
    [self.dateFormatter setDateFormat:@\"yyyy\'-\'MM\'-\'dd\'T\'HH\':\'mm\':\'ss\'Z\'\"];



... 

else if([elementName isEqualToString:kUpdated]){
    self.currentQuestion.updated = [self.dateFormatter dateFromString:self.currentParsedCharacterData ];
}

Any help greatly appreciated. Thanks!

**Based on the link reference from theChrisKent I fixed the problem like so:

else if([elementName isEqualToString:kLastOnDeck]){

    NSString *dateStr = self.currentParsedCharacterData;
    // we need to strip out the single colon
    dateStr = [dateStr stringByReplacingOccurrencesOfString:@\":\" 
                                                 withString:@\"\" 
                                                    options:0 
                                                      range:NSMakeRange([dateStr length] - 5,5)];




    self.currentQuestion.lastOnDeck = [dateFormatter dateFromString:dateStr];

}

回答1:

You don't need near as many single quotes as you have (only needed on non date/time characters), so change this:

[self.dateFormatter setDateFormat:@"yyyy'-'MM'-'dd'T'HH':'mm':'ss'Z'"];

To this:

[self.dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ssZZZ"];
...
self.currentQuestion.updated = [self.dateFormatter dateFromString:[self.currentParsedCharacterData stringByReplacingOccurrencesOfString:@":" withString:@"" options:0 range:NSMakeRange([self.currentParsedCharacterData length] – 5,5)]];

Documentation here: https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/DataFormatting/Articles/dfDateFormatting10_4.html#//apple_ref/doc/uid/TP40002369-SW1

Unicode Format Patterns: http://unicode.org/reports/tr35/tr35-6.html#Date_Format_Patterns

Dealing with TimeZones with Colons (+00:00): http://petersteinberger.com/2010/05/nsdateformatter-and-0000-parsing/

回答2:

I was having the same problems with the colon at the end. Here's a function I used to normalize the date to make NSDate happy.

/**
 * Timezones are returned to us in the format +nn:nn
 * The date formatter currently does not support IS 8601 dates, so
 * we convert timezone from the format "+07:30" to "+0730" (removing the colon) which
 * can then be parsed properly.
 */
- (NSString *)applyTimezoneFixForDate:(NSString *)date {
    NSRange colonRange = [date rangeOfCharacterFromSet:[NSCharacterSet characterSetWithCharactersInString:@":"] options:NSBackwardsSearch];
    return [date stringByReplacingCharactersInRange:colonRange withString:@""];
}

回答3:

It took me a while to find the simple answer for this. and there are a lot of solutions that involve bringing in extra third party code.

For those who are struggling with this now and are only supporting iOS 6 and above.

You can set the date formatter to

[dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ssZZZZZ"]

And this will properly handle the "-05:00" with the colon.

回答4:

Solutions is to change :

[self.dateFormatter setDateFormat:@"yyyy'-'MM'-'dd'T'HH':'mm':'ss'Z'"];

To this notation :

[self.dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss'Z'"];

i hope it will help you.

回答5:

ISO8601DateFormatter

I've had great success with this library which is available as a CocoaPod.

https://github.com/boredzo/iso-8601-date-formatter

Usage

- (ISO8601DateFormatter *)dateFormatter
{
    static ISO8601DateFormatter *dateFormatter = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        dateFormatter = [[ISO8601DateFormatter alloc] init];
        dateFormatter.includeTime = YES;
    });

    return dateFormatter;
}


NSDate *date = [[self dateFormatter] dateFromString:@"2015-05-09T13:06:00"];

回答6:

The problem is the 'Z' at the end. The way you are writing it within quotes, your parser expects a literal character Z in your time string, and there isn't one. What you want is the Z formatting character without quotes, which indicates that your time string contains time zone information. Which it does, the -05:00 at the end of your string is the time zone.

Since you expect time zone information, setting the time zone in your date formatter is rather pointless. And check the link to the Unicode formatting patterns, that link contains the definitive information that you should trust above all answers you get here.

回答7:

As of iOS 10 the system provided NSISO8601DateFormatter is available for this particular format.

来源：https://stackoverflow.com/questions/4999396/how-to-parse-a-date-string-into-an-nsdate-object-in-ios

标签

iphone

objective-c

ios

nsdate

nsdateformatter