How do I load multiple arrays into an NSDictionary object (Objective-C; iPhone SDK)?

Question

This method doesn't work...but when I move away from returning a dictionary object and return a single array to the table data source, it works perfectly. so the error of my ways is in how i am creating this dictionary...

Any Help?

- (NSDictionary *) returnDictionary {
self.shopNameArray = [[NSArray alloc] arrayWithObjects: @"Item 1", @"Item 2", @"Item 3", nil];
self.shopLocationArray = [[NSArray alloc] arrayWithObjects: @"Cincinnati, OH", @"Phoenix, AZ", @"Tuscon, AZ", nil];
self.shopImageArray = [[NSArray alloc] arrayWithObjects: @"image1", "image2", @"image3", nil];

NSMutableDictionary *theDictionary = [[NSMutableDictionary alloc] retain];

[theDictionary setObject:shopNameArray forKey:@"Shop Name"];
[theDictionary setObject:shopLocationArray forKey:@"Shop Location"];
[theDictionary setObject:shopImageArray forKey:@"Shop Image"];

return theMechanicDictionary;
}

Thanks.

Answer 1

Change

[[NSDictionary alloc] retain]

to

[[NSMutableDictionary alloc] retain]

Answer 2

You need to call arrayWithObjects: on NSArray directly, not on an instance of NSArray. So use [NSArray arrayWithObjects: @"Item 1", @"Item 2", @"Item 3", nil]; instead of [[NSArray alloc] arrayWithObjects: @"Item 1", @"Item 2", @"Item 3", nil];.

Also change [[NSDictionary alloc] retain] to [NSMutableDictionary arrayWithCapacity:0], so you're returning an autoreleased NSMutableDictionary. Also, you should always call [[SomeClass alloc] init] or [[SomeClass alloc] initWith...], not [[SomeClass alloc] someMethod], that doesn't work.

It looks to me like you don't really understand what methods are supposed to be called on what exactly...

Answer 3

Fixed block of code:

- (NSDictionary *) returnDictionary {
    self.shopNameArray = [NSArray arrayWithObjects: @"Item 1", @"Item 2", @"Item 3", nil];
    self.shopLocationArray = [NSArray arrayWithObjects: @"Cincinnati, OH", @"Phoenix, AZ", @"Tuscon, AZ", nil];
    self.shopImageArray = [NSArray arrayWithObjects: @"image1", "image2", @"image3", nil];

    NSMutableDictionary *theDictionary = [NSMutableDictionary dictionary];

    [theDictionary setObject:self.shopNameArray forKey:@"Shop Name"];
    [theDictionary setObject:self.shopLocationArray forKey:@"Shop Location"];
    [theDictionary setObject:self.shopImageArray forKey:@"Shop Image"];

    return theDictionary;

}

Changes made:

1. [NSArray arrayWithObjects:… is the format for the particular class method you are trying to call.
2. [NSMutableDictionary dictionary] is the easiest way to get an autoreleased mutable dictionary. Like @Douwe suggested, you may want to init this object with a starting size of 3, but that's not necessary. It only makes a difference if you're loading a butt-ton of objects into your dictionary and you don't want it to continuously be resizing itself.
3. When adding the arrays to your dictionary, you shouldn't reference them by the name of the iVar. Since you set the arrays using properties (self.shopNameArray =) the name of the iVar will not necessarily be the same.