Question

How can I pass a “MutableArray with full of Objects” to another class by using NSUserDefaults? I know how to pass “MutableArray“s but this does not work!

So;

I have a MutableArray; ‘myCityObjects‘, and I populate it with objects; ‘cities‘
In each ‘cities‘ object there are properties like cityName, cityLocation etc…

[myCityObjects addObject:cities];

Now, what I want to do is to pass this MutableArray (filled with objects) to another class by using ‘NSUserDefaults‘;

[[NSUserDefaults standardUserDefaults] setObject: myCityObjects forKey:@"MCO"];

And in the other class,

NSMutableArray *getMyCityObjects = [[NSArray alloc] init];

getMyCityObjects = [[NSUserDefaults standardUserDefaults] mutableArrayValueForKey:@"MCO"];

But it doesn’t work! I cannot get myCityObjects in the other class, “getMyCityObjects” is empty. How can I fix that?

Thanks,
E.

Answer 1

Your array is nil because the objects in it (your custom objects) can’t be serialised.

Please take a look at the NSCoding protocol. Objects you want to serialise (eg for writing to NSUserDefaults) must implement the methods -encodeWithCoder: and -initWithCoder.

I’m sure you’ll find how this is rather easily done searching for the terms I gave you…