从数组中删除字典元素（plist）Cocoa Touch

Question

Hey guys, I have this plist:

    <plist version="1.0">
    <dict>
        <key>Rows</key>
        <array>
            <dict>
                <key>FavTitle</key>
                <string>Book1</string>
                <key>Favourited</key>
                <string>duh</string>
                <key>SaveName</key>
                <string>book1.pdf</string>
            </dict>
            <dict>
                <key>FavTitle</key>
                <string>Book2</string>
                <key>Favourited</key>
                <string>duh</string>
                <key>SaveName</key>
                <string>book2.pdf</string>
            </dict>
        </array>
    </dict>
    </plist>

which populates my UITableView like so:

cell.text = [dictionary objectForKey:@"FavTitle"];

(yeah yeah thats depreciated) and when a cell is selected, my dictionary objects are pushed to my detail view (eg to set Title and UIWebView url) like so:

NSDictionary *dictionary = [self.tableDataSource objectAtIndex:indexPath.row];
        DetailViewController *dvController = [[DetailViewController alloc] initWithNibName:@"DetailView" bundle:[NSBundle mainBundle]];
        dvController.selectedSaveName = [dictionary objectForKey:@"SaveName"];
        dvController.selectedFavTitle = [dictionary objectForKey:@"FavTitle"];
        dvController.selectedFavourited = [dictionary objectForKey:@"Favourited"];
        [dvController setHidesBottomBarWhenPushed:YES];

        [self.navigationController pushViewController:dvController animated:YES];


        [dvController release];

Thats all fine and dandy and I can add to that array, but how do I take the current loaded dictionary from it? This isn't working:

NSString *documentsDirectory = [[NSString alloc] initWithString:[[[[NSBundle mainBundle]  resourcePath] stringByDeletingLastPathComponent] stringByAppendingPathComponent:@"Documents/"]];
    NSString *writablePath = [documentsDirectory stringByAppendingPathComponent:@"Favourites.plist"];
    NSMutableDictionary *rootDict = [[NSMutableDictionary alloc] initWithContentsOfFile:writablePath];
    NSMutableDictionary *thisFav = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"duh", @"Favourited",
                                  selectedSaveName, @"SaveName",
                                  selectedFavTitle, @"FavTitle",
                                  nil];
    [[rootDict objectForKey:@"Rows"] removeObject:thisFav];      
    [rootDict writeToFile:writablePath atomically: YES];

How could I remove the entry that has the string 'Book2'? The last snippet I've posted doesn't work! Thanks guys!

Answer 1

You don't say what error, if any, you are getting. However your problem might be with mutability.

When you read in a plist to an NSMutableDictionary using initWithContentsOfFile only the top-level dictionary itself is mutable, any nested containers are immutable - in your case the Rows array would be immutable.

To make the whole thing mutable you need to use propertyListFromData:mutabilityOption:format:errorDescription: from NSPropertyListSerialization passing in NSPropertyListMutableContainers or NSPropertyListMutableContainersAndLeaves as the mutability option.