CODEWITHSUNDEEP
iosobjective-cnsuserdefaults
Karlo A. López
Karlo A. López

Reputation: 2668

How to see if a NSUserdefaults is nil or not?

Well I dont know if my title is well drafted but I will try to explain whats my problem, I want to save a NSDate for an IndexPath in NSUserDefaults, this happens when viewWillDisappear but its crashing, its saving correctly because when I reopen the DatePicker loads the date I want but still crash when saving a date at the UserDefaults So heres my code so you can see whats going on....

I read if the NSUserDefaults is nil or not so I can load the DatePicker:

    NSArray *indexParams = [self.userdefaults objectForKey:@"indexpath"];
NSIndexPath *myIndexPath = [NSIndexPath indexPathForRow:indexParams[1]
                                              inSection:indexParams[0]];

self.notificationDate = [self.userdefaults objectForKey:@"date"];
NSDate *date = [self.userdefaults objectForKey:[NSString stringWithFormat:@"%d", myIndexPath.row]];

if(date){
    [self.NotSwith setOn:YES];
    self.DatePicker.date = [self.userdefaults objectForKey:[NSString stringWithFormat:@"%d", myIndexPath.row]];



}else{
    [self.NotSwith setOn:NO];


    }

When I want to save the date in viewWillDisappear its when the crash happens:

NSArray *indexParams = [self.userdefaults objectForKey:@"indexpath"];
NSIndexPath *myIndexPath = [NSIndexPath indexPathForRow:indexParams[1]
                                              inSection:indexParams[0]];

NSDate *date = [self.userdefaults objectForKey:[NSString stringWithFormat:@"%d", myIndexPath.row]];

if(date){
//    [self.userdefaults synchronize];


}

else{
    [self.userdefaults setObject:self.DatePicker.date forKey:[NSString stringWithFormat:@"%d", myIndexPath.row]];
    [self.userdefaults synchronize];
    [[UIApplication sharedApplication] scheduleLocalNotification:local];


}

But the info its saved successfully and the date picker loads the date in relaunch.

crash log:

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSPlaceholderArray initWithObjects:count:]: attempt to insert nil object from objects[0]'

So hope I explained well, Thanks!

Setting the indexpath:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{



    NSNumber *section = [NSNumber numberWithInt:indexPath.section];
    NSNumber *rows = [NSNumber numberWithInt:indexPath.row];

    [self.userdefaults setObject:@[section, rows] forKey:@"indexpath"];
}

Upvotes: 1

Views: 471

Answers (1)

danh
danh

Reputation: 62686

Sounds like you want to save both the selected index path and a date. Saving a date in NSUserDefaults is easy.

// no need to keep a property on self for user defaults.  you don't need to keep
// that around.  just a stack variable will work.
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSDate *date = [NSDate date];

[defaults setObject:date forKey:@"myDate"];
[defaults synchronize];

Get it back later on this way:

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSDate *date = [defaults objectForKey:@"myDate"];

// if nothing has been stored using that key then objectForKey will return nil
if (date) {
    // it's there!
} else {
    // it's not there
}

Storing an index path is a little more tricky, but this will work:

// wrap your row and section in NSNumbers, wrap those in an array for brevity
NSNumber *section = [NSNumber numberWithInt:myIndexPath.section]; 
NSNumber *row = [NSNumber numberWithInt:myIndexPath.row];

[defaults setObject:@[section, row] forKey:@"myIndexPath"];  // then synchronize

// naturally, when you get it later, you can check for nil again, and,
// if it's not nil, to rebuild the index path...

NSArray *indexParams = [defaults objectForKey:@"myIndexPath"];
NSIndexPath *myIndexPath = [NSIndexPath indexPathForRow:indexParams[1]
                                              inSection:indexParams[0]];

The key is what isn't in this answer: no NSData, no NSKeyedArchiver, no string manipulation to build an index path representation. Best of luck.

Upvotes: 2

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