Retrieving NSDate from NSUserDefaults always returns nil

Question

I have an NSDate that I am saving into NSUserDefaults.

When my app runs this code for a 2nd pass, I am expecting an NSDate to be retrieved from NSUserDefaults but, it is always nil. Not sure why.

NSDate *mostRecentMentionDate = [dateFormatter dateFromString:mostRecentMentionMessageTimestamp];
NSDate *savedMentionDate = [[NSUserDefaults standardUserDefaults] objectForKey:@"mostRecentMentionDate"];

if (savedMentionDate == nil || [savedMentionDate isEqual:[NSNull null]]) {
    //There is no existing mention, so save the most recent one
    [[NSUserDefaults standardUserDefaults]setObject:mostRecentMentionDate forKey:@"mostRecentMentionDate"];
    [[NSUserDefaults standardUserDefaults] synchronize];
}

You do not need to convert the `NSDate` to/from a string, `NSUserDefaults` is perfectly capable of storing `NSDate` objects, and you're just making things complicated and slow by doing the conversion yourself. See http://stackoverflow.com/questions/2013850/whats-the-optimum-way-of-storing-an-nsdate-in-nsuserdefaults — Abhi Beckert, Nov 10 '11 at 08:22
My date originally comes in as a String, thats why I have to turn it into an NSDate via dateFromString: — Sheehan Alam, Nov 10 '11 at 16:45
`if (savedMentionDate == nil || [savedMentionDate isEqual:[NSNull null]])` - This check is entirely redundant. Just check if it's equal to nil and call it a day. — sudo rm -rf, Nov 28 '11 at 17:49

score 1 · Answer 1 · edited Nov 10 '11 at 08:27

if i use this code it work fine i think problem with your dateformater

NSDate *mostRecentMentionDate = [NSDate date];
NSDate *savedMentionDate = [[NSUserDefaults standardUserDefaults] objectForKey:@"mostRecentMentionDate"];

if (savedMentionDate == nil || [savedMentionDate isEqual:[NSNull null]]) {
  //There is no existing mention, so save the most recent one
  [[NSUserDefaults standardUserDefaults]setObject:mostRecentMentionDate forKey:@"mostRecentMentionDate"];
  [[NSUserDefaults standardUserDefaults] synchronize];
}

score 1 · Accepted Answer · answered Nov 10 '11 at 08:03

1

Are you sure you're getting a valid object for mostRecentMentionDate? Put it into NSLog right before fetching savedMentionDate from NSUserDefaults, you might be having problems with date format.

answered Nov 10 '11 at 08:03

Eugene

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iOSPawan · Answer 3 · 2011-11-10T08:23:48.890

NSDate confirm to NSCoding protocol. above code should work.

Try this -

/

/ Create and store it
NSDate * date = [NSDate date];
NSData * dateData = [NSKeyedArchiver archivedDataWithRootObject:date];
[dateData writeToFile:@"/Some/path/to/file.dat" atomically:NO];

// Now bring it back
NSData * restoredDateData = [NSData dataWithContentsOfFile:@"/Some/path/to/file.dat"];
NSDate * restoredDate = [NSKeyedUnarchiver unarchiveObjectWithData:restoredDateData];

Or you Can get timeIntervalSinceReferenceDate value as a NSNumber (double) and save it to NSUserDefault to keep track of previous date.

Retrieving NSDate from NSUserDefaults always returns nil

3 Answers3