iOS - NSMutableDictionary reverting to previous state? - ios

Question

I'm trying to make a "Delete" button on an "Edit Item" page, which when pressed will go back and remove the relevant entry in an NSMutableDictionary on the previous page, and then update the tableview list of entries.
It starts with an IBAction method on the "Edit Item" page, which basically does nothing but feed the key to be deleted back to the controller for the previous page:
- (IBAction)deleteItem:(id)sender {
[_parentController removeItemWithDeleteButton:[_mainFactoidTextField text]];
}
which is where the action actually starts (on the list page):
- (void)removeItemWithDeleteButton:(NSString *)key {
[_currentItemsDict removeObjectForKey:key];
[self.navigationController popViewControllerAnimated:YES];
}
At the start of that method, _currentItemsDict has 8 objects, which drops to 7 after removeObjectForKey: is called. Then it pops off the top ViewController, which is the "Edit Item" page, returning us to the list of entries.
Then when that method is done, the breakpoint immediately jumps to:
- (void)viewWillAppear:(BOOL)animated {
NSArray *tempArray = [NSArray arrayWithArray:[_currentItemsDict allKeys]];
NSArray *sortedArray = [tempArray sortedArrayUsingSelector:#selector(caseInsensitiveCompare:)];
_currentItemsArray = [NSMutableArray arrayWithArray:sortedArray];
[_tableView reloadData];
}
But by the first line of viewWillAppear:, _currentItemsDict has reverted back to 8 objects. Everything works fine from then on, but it's all working with the original 8 entries, meaning that nothing got deleted.
From my limited experience with these sorts of things (I'm definitely still a beginner), I'm going to guess this has something to do with the popViewControllerAnimated: method, but I cannot figure out what. I've heard distantly of certain variables being stored in different ways that might make them come back as an earlier version of themselves, but I haven't wrapped my mind around the concept. Or maybe it's something else entirely, I don't know. All I can tell is that _currentItemDict has 7 objects, and then one line later it has 8 again.
Can anyone help out a new guy, and explain where I'm going wrong? Or if it's easier, can you suggest a better solution for removing an entry in an NSMutableDictionary from a different ViewController? (Code samples and tutorial links are much appreciated, as I'm currently just noobish enough to sometimes be unable to translate theory into practice on my own!)
Thank you in advance for your help!

Answer 1

Do you know how properties work in Objective-C 2.0? I would declare a property in your parentViewController to contain your _currentItemsArray, declared as a strong reference.
#property (nonatomic,strong) NSMutableArray *_currentItemsArray;
Also, set a weak property in your childViewController (the one you push to for deletion)
#property (nonatomic, weak) NSMutableArray *parentItemsArray;
Set the property on the childViewController upon push
childViewController.parentItemsArray = self._currentItemsArray;
[self.navigationController pushViewController:childViewController animated:YES];
Remove the item inside the array within childViewController instead of calling a method on your parentController
[self.parentItemsArray removeObjectAtIndex:indexOfKey];
Doing this, you don't have to sort the array again in viewWillAppear. Instead, just ask the tableView to reloadData
Does any of this make sense?
It also may be wise to include your logic inside cellForRowAtIndexPath, numberOfRowsInSection and the other tableViewDataSource methods.