Program crashing when adding object to NSArray

Question

I have the following IBAction set up:

#define FAVORITES_KEY @"GraphViewController.Favorites"
- (IBAction)addToFavorites:(id)sender {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSMutableArray *favorites = [defaults objectForKey:FAVORITES_KEY];
    if (!favorites) favorites = [NSMutableArray array];
    [favorites addObject:self.program];
    [defaults setObject:favorites forKey:FAVORITES_KEY];
    [defaults synchronize];
}

The first time this action is called it all works well, the object is added to my array and saved to NSUserDefaults without a problem, after that first call it will throw an exception when adding to the favorites array, if I try to step over the break it will say this:

Single stepping until exit from function objc_exception_throw, 
which has no line number information.

Catchpoint 3 (exception thrown).

Anyone had a similar issue or might know what's happening?

Costique · Accepted Answer · 2012-02-10 19:34:20Z

4

NSUserDefaults returns an immutable array, so you need to convert it:

NSMutableArray *favorites = [[defaults objectForKey:FAVORITES_KEY] mutableCopy];
if (!favorites) favorites = [NSMutableArray new];
...
[favorites release];

answered Feb 10, 2012 at 19:34

Costique

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1 Comment

8vius Over a year ago

That did it, small details like that are good to know. Gotta remember iOS always works with unmutable copies

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