integerForKey: always returns zero

Question

Hi,

i'm trying to retrieve a value from my preference file which is an integer. The funny thing is that it always returns zero, although it does exist and the names for both integerForKey: and setIntegerForKey: are the same.

Here's how I retrieve the value: [defaults integerForKey:@"BackUpSize"];

And here I set it: [defaults setInteger:[sizeSlider doubleValue]*8589934592 forKey:@"BackUpSize"];

I'm stunned. It should work...or am I missing something here?

Thanks

Edit: defaults is created as such: NSUserDefaults*defaults = [NSUserDefaults standardUserDefaults];

Edit: I've tried creating my own NSUserDefaults method for this issue, but it still returns zero.

-(void)setDouble:(double)dou forKey:(id)key
{
    [[NSUserDefaults standardUserDefaults] setObject:[NSNumber numberWithDouble:dou] forKey:key];
}
-(double)doubleForKey:(id)key
{
    return [[[NSUserDefaults standardUserDefaults] objectForKey:key] doubleValue];
}

Answer 1

You're passing a double into something that expects an integer. Normally you'd expect some truncation to occur, and to end up with an int, but you can't guarantee that the setInteger:forKey: method is doing that for you.

Why are you multiplying your slider value by that apparently arbitrary number?

Edit:

To explain my answer a little more:

In order to store numbers in the defaults they need to be wrapped in NSNumber objects. setInteger:forKey, et al, are convenience methods that probably just take your integer and create an NSNnumber from it, using numberWithInt:. I can't be 100% sure because I haven't seen Apple's code, but I'd assume that passing a double to numberWithInt: will return nil because a double is not an int.

Answer 2

8589934592 is a hard-coded literal? Really? You should at least put something like 1 << 33. Even then, declare it as a constant, for crying out loud.

If you're building for 32 bit, NSInteger is a 32 bit signed value. So you are rather likely to be overflowing. I'm not sure what the behaviour of NSUserDefaults would be in that case, but it's worth considering.