从TableView行向NSMutableDictionary添加值

Question

I'm trying to build a function that will check if a retrieved JSON value have changed ( messagecount in a given conversation). I'm populating a TableView with my JSON data and I would like to store the value in a dictionary and compare them later when I do a data update.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
ConversationsModel* conversation = _feed.conversations[indexPath.row];
static NSString *identifier = @"ConversationCell";
UITableViewCell *cell = [_tableView dequeueReusableCellWithIdentifier:identifier forIndexPath:indexPath];   
if (cell == nil){
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault
                                      reuseIdentifier:identifier];
}
[self getMessageCountToDictionary:conversation.messagecount id:conversation.conversationid];
cell.textLabel.text = conversation.title;  
return cell; 
}

And my method to store the values in a NSMutableDictionary:

- (void)getMessageCountToDictionary:(NSNumber*)messagecount id:(NSString *)conversationid 
{
NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init];
if (conversationid != NULL) {      
[dictionary setValue:conversationid forKey:[NSString stringWithFormat:@"%@", conversationid]];
[dictionary setValue:messagecount forKey:@"messageCount"];
dictionaryCopy =  [dictionary mutableCopy];
}
NSLog(@"Stored in dictionary %lu", (unsigned long)dictionary.count);
}

NSLog returns 2

Well, I'm not sure if I'm on the right track here for what I intend to do. All inputs are highly appreciated.

Answer 1

I would recommend to use key-value observer to watch your objects changing values.

You can read more about it here:

https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/KeyValueObserving/KeyValueObserving.html