NSString to NSDate

I got a string that contains the current date by using this :

NSString *date = [[NSDate date] description];

At a different point I want to retrieve the date from this string and I used the following code:

[NSDateFormatter setDefaultFormatterBehavior:NSDateFormatterBehavior10_4];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
//[NSDateFormatter setDefaultFormatterBehavior:NSDateFormatterBehaviorDefault];
[dateFormatter setDateFormat:@"YYYY-MM-DD HH:MM:SS ±HHMM"];

NSDate *dateFromString = [[NSDate alloc] init];
dateFromString = [dateFormatter dateFromString:<NSString containing date>];

I am getting dateFromString as nil 0x0. What am I doing wrong?

Solution 1:

You can't invent format string syntax and expect it to work; you need to actually use a documented format. (Seriously, "MM" meaning "month", "minute" and "GMT offset minutes" all at the same time?)

As the documentation points out, the 10.4 formatters use Unicode format strings.

Try "yyyy-MM-dd HH:mm:ss ZZZ" instead.

Also, Objective-C source is ASCII. Don't put characters like ± in there and expect it to work in any context; instead, use strings files.

Solution 2:

Also, dateFromString: returns an autoreleased NSDate, so:

NSDate *dateFromString = [[NSDate alloc] init]; // <- non freed instance
dateFromString = [dateFormatter dateFromString:<NSString containing date>]; // <- new autoreleased instance
....
[dateFromString release]; // <- wrong

You may want to:

//NSDate *dateFromString = [[NSDate alloc] init];
NSDate *dateFromString = [dateFormatter dateFromString:<NSString containing date>];
....
//[dateFromString release]; // dateFromString is autoreleased

Hope this could save someone :)

Solution 3:

Made an NSString extension for that.

// Simple as this.   
date = dateString.dateValue;

Thanks to NSDataDetector, it recognizes a whole lot of format.

// Tested in GMT+1 (Hungary).
@"2014-01-16" dateValue is <2014-01-16 11:00:00 +0000>
@"2014.01.16" dateValue is <2014-01-16 11:00:00 +0000>
@"2014/01/16" dateValue is <2014-01-16 11:00:00 +0000>
@"2014 Jan 16" dateValue is <2014-01-16 11:00:00 +0000>
@"2014 Jan 16th" dateValue is <2014-01-16 11:00:00 +0000>
@"20140116" dateValue is <2014-01-16 11:00:00 +0000>
@"01-16-2014" dateValue is <2014-01-16 11:00:00 +0000>
@"01.16.2014" dateValue is <2014-01-16 11:00:00 +0000>
@"01/16/2014" dateValue is <2014-01-16 11:00:00 +0000>
@"16 January 2014" dateValue is <2014-01-16 11:00:00 +0000>
@"01-16-2014 17:05:05" dateValue is <2014-01-16 16:05:05 +0000>
@"01-16-2014 T 17:05:05 UTC" dateValue is <2014-01-16 17:05:05 +0000>
@"17:05, 1 January 2014 (UTC)" dateValue is <2014-01-01 16:05:00 +0000>

Part of eppz!kit, grab the category NSString+EPPZKit.h from GitHub.

ORIGINAL ANSWER: Whether you're not sure (or just don't care) about the date format contained in the string, use NSDataDetector for parsing date.

//Role players.
NSString *dateString = @"Wed, 03 Jul 2013 02:16:02 -0700";
__block NSDate *detectedDate;

//Detect.
NSDataDetector *detector = [NSDataDetector dataDetectorWithTypes:NSTextCheckingAllTypes error:nil];
[detector enumerateMatchesInString:dateString
                           options:kNilOptions
                             range:NSMakeRange(0, [dateString length])
                        usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop)
{ detectedDate = result.date; }];

Solution 4:

You might check out TouchTime.

https://github.com/jheising/TouchTime.

It's a direct port of the awesome strtotime function in PHP in 5.4 for Cocoa and iOS. It will take in pretty much any arbitrary format of date or time string and convert it to an NSDate.

Hope it works, and enjoy!