NSMutableArray in NSUserDefault - nsmutablearray

Question

i've a problem with my table!
i use a parsing tableview but when i change view, my table loses data. So i decide to save all data to nsuserdefault; but, here the problem, NSUserDefault warns me:
"Note that dictionaries and arrays in property lists must also contain only property values."
NB: itemsToDisplay is a NSMutableArray and contain title, url, data and summary of parsedItems.
Well, here my code:
self.itemsToDisplay = [[[NSUserDefaults standardUserDefaults] arrayForKey:#"items"] mutableCopy];
if (!self.itemsToDisplay) {
self.itemsToDisplay = [[NSMutableArray alloc] init];
}
self.itemsToDisplay = [[NSMutableArray alloc]init];
self.itemsToDisplay = [parsedItems sortedArrayUsingDescriptors:
[NSArray arrayWithObject:[[[NSSortDescriptor alloc] initWithKey:#"date"
ascending:NO] autorelease]]];
[[NSUserDefaults standardUserDefaults] setObject:self.itemsToDisplay forKey:#"items"];
[[NSUserDefaults standardUserDefaults] synchronize];
I suppose the problem is setObject:self.itemsToDisplay, but i don't know how solve it.
Thank You guys..

Answer 1

First lets mention that the table cannot lose data because it does not hold any user data. The data is either provided through bindings or through delegation see NSTableViewDataSource in Apples documentation).
Second, the first three assignments to self.itemsToDisplay serve no purpose (unless you have side-effects in the setter) because they are all overridden by the last assignment.
Finally, if this code is already in the delegate then the delegate should be instantiated in your NIB file for the data to survive past a view swap. If your delegate is an object that is instantiated with your view it will also die with it along with all of the data and writing to the user-defaults is a bad idea for what you are trying to achieve. Simply set the delegate to an object whose lifetime is greater than that of both views.

Answer 2

self.itemsToDisplay = [parsedItems sortedArrayUsingDescriptors:
[NSArray arrayWithObject:[[[NSSortDescriptor alloc] initWithKey:#"date"
ascending:NO] autorelease]]];
//First lets encode it
NSUserDefaults *userDefault=[NSUserDefaults standardUserDefaults];
NSData *myEncodedObject = [NSKeyedArchiver archivedDataWithRootObject:self.itemsToDisplay];
[userDefault setObject:myEncodedObject forKey:[NSString stringWithFormat:#"sample"]];