使用自定义顺序对NSArray进行排序

Question

I have an NSMutableDictionary object that contains a list of menu items for an iPhone app. The desired order of the menu items is not alphabetical so the standard way of sorting the keys is not really an option. My dictionary is as follows and is initialized in the desired order (I understand that dictionaries are not sorted--I need to sort the array of keys in this order):

    menuDict = [[NSMutableDictionary alloc] init];
    [menuDict setObject:@"Main Menu" forKey:@"EntryViewController"];
    [menuDict setObject:@"States Lookup" forKey:@"AllStatesViewController"];
    [menuDict setObject:@"Favorites" forKey:@"FavoritesViewController"];
    [menuDict setObject:@"Help" forKey:@"HelpViewController"];
    [menuDict setObject:@"About" forKey:@"AboutViewController"];

How can I get a list of keys and sort them in the same order as this dictionary ? Thanks!

Answer 1

You can't, NSDictionary does not save the order in which items are added. For this you should use a NSArray .

Here is an example of how you can us it:

NSArray *menuArray = @[
   @{ @"Title" : @"Main Menu", @"Controller" : @"EntryViewController"},
   @{ @"Title" : @"States Lookup", @"Controller" : @"AllStatesViewController"},
   @{ @"Title" : @"Favorites", @"Controller" : @"FavoritesViewController"},
   @{ @"Title" : @"Help", @"Controller" : @"HelpViewController"},
   @{ @"Title" : @"About", @"Controller" : @"AboutViewController"},
];

This way you can even add an extra key in the dictionary for the order, so you can sort it later if you need to insert items later in the menu.

Answer 2

Create an array of keys and another of values. Then use the dictionaryWithObjects:forKeys: method to create your dictionary. Then you don't need to do any additional sorting because you have the array of keys.

As has been pointed out, you can't get the ordered keys back from the dictionary so you need to use the original array of keys for your order information.