Accessing an Array of Dictionarys?

Question

I have a couple of questions regarding the code below:

(1) Is "newItem" an autoreleased object? Its getting a returned dictionary from the specified array index?

(2) Is there a simple way to access an array of dictionarys in one hit, or am I doing it the way you would expect?

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    NSMutableArray *menu = [[NSMutableArray alloc] init];
    NSMutableDictionary *menuItem;
    NSMutableDictionary *newItem;

    NSArray *itemName = [NSArray arrayWithObjects:
         @"Latte Medio",
         @"Cappucion Medio",
         @"Mocha Medio",
         @"Vanilla Latte Medio",nil];

    NSArray *itemFat  = [NSArray arrayWithObjects:     
         [NSNumber numberWithFloat:6.9],
         [NSNumber numberWithFloat:4.7],
         [NSNumber numberWithFloat:6.6],
         [NSNumber numberWithFloat:6.9],nil];

    NSArray *itemCals = [NSArray arrayWithObjects: 
         [NSNumber numberWithInt:516],
         [NSNumber numberWithInt:408],
         [NSNumber numberWithInt:624],
         [NSNumber numberWithInt:743],nil];

    NSLog(@"DICTARRAY ... Start");

    // Create menuItem object
    menuItem = [[NSMutableDictionary alloc] init];
    [menuItem setObject:[itemName objectAtIndex:0] forKey:@"product"];
    [menuItem setObject:[itemFat objectAtIndex:0] forKey:@"fat"];
    [menuItem setObject:[itemCals objectAtIndex:0] forKey:@"calories"];

    // Add menuItem object to menu
    [menu addObject:menuItem];
    [menuItem release], menuItem = nil;

    // Access menu to get menuItem
    newItem = [menu objectAtIndex:0];
    NSLog(@"DATA: %@",[newItem objectForKey:@"product"]);
    NSLog(@"DATA: %@",[newItem objectForKey:@"fat"]);
    NSLog(@"DATA: %@",[newItem objectForKey:@"calories"]);

    // Clean up
    [menu release], menu = nil;
    [pool drain];
    return 0;
}

gary

Answer 1

The way you're storing this information seems odd. You're storing all the names together, all the fat together, and all the calories together, when really the items (or objects) you're dealing with are coffee drinks. It would probably be easier to make a new object, let's say CoffeeDrink, that looked something like the following:

@interface CoffeeDrink:NSObject {
    NSString *name;
    NSNumber *fat;
    NSNumber *calories;
}

@property( retain ) NSString *name;
@property( retain ) NSNumber *fat;
@property( retain ) NSNumber *calories;

@end

Then, in your code, you could have an NSArray of different CoffeeDrinks.

Answer 2

newItem is not an autoreleased object, it looks to be a pointer to menuItem, which is (also) not autoreleased.

I assume you are forced to store this information as arrays for some reason or another, and you are not deliberately trying to make your life more difficult. In that sense, you can still simplify things a bit.

You could do it all in-line, but that would probably turn into "the line of code from hell". I would probably write it is like this (pseudo-code)

NSMutableDictionary* childDictionary  = // .. make the dictionary

// for each NSArray a
{
  NSString* k = // ... arbitrary key
  NSArray* a = [NSArray arrayWithObjects:// ... make the array with objects];
  [childDictionary addObject:a forKey:k];
}

// stuff it into the parent
NSDictionary* parentDictionary = [NSDictionary withObjects:childDictionary, nil forKeys:@"root"];

Answer 3

in obj-c, the apple guidelines are, generally, when a method/object returns an object that you need to eventually release yourself, the method name will start with "new," "copy," i.e.:

newArray
copyArray

when adding things to an NSArray or NSDictionary, they'll get retained and managed by those arrays or dictionaries. the items you put in them will get a release message when you release the array or dictionary holding your items.