Question

Throughout my iOS program. I create multiple arrays that all work together to make the program work. Now I need a method to store the arrays even when the iPhone is turned off. So I need these arrays to be stored like files that only I can touch.

I really would like to use User Defaults, but I just don’t know if that is what I need. I have questions like:

1. How long will my data last in User Defaults?
2. When could you possibly lose the data?

If I was able to store arrays in User Defaults, how might I go about storing arrays in NSDictionaries? That way I could keep of my associated arrays together and give each array a specific key.

Answer 1

store array as NSData as in NSDefaults

[[NSUserDefaults standardUserDefaults] setObject:[NSKeyedArchiver archivedDataWithRootObject:urArray1] forKey:@"Array1"];

[[NSUserDefaults standardUserDefaults] setObject:[NSKeyedArchiver archivedDataWithRootObject:urArray2] forKey:@"Array2"];

and read it as

 NSData *dataRepresentingSavedArray = [[NSUserDefaults standardUserDefaults] objectForKey:@"Array1"];
 if (dataRepresentingSavedArray != nil)
      NSArray *oldSavedArray = [NSKeyedUnarchiver unarchiveObjectWithData:dataRepresentingSavedArray];