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iOS Build a Simple iPhone App with Objective-C Creating a Data Model Creating a Data Collection

No idea how to do this.

Let's add a few items section (task 2) for the Creating a Data Collection challenge. It is asking me to use 'self' and dot notation to initialize an array of three items to shoppingList.

Usage of 'self' in lesson much more limited. I don't remember much instruction on how much we treat self (and dot syntax) in the Objective-C Basics, and certainly not whether many of the same operations as are used in bracket syntax can just be dropped in. Even Googling 'self in Objective-C' or using the documentation is not giving me the answer.

What am I missing? I have tried including NSArray in brackets, not including it, various dot-suffixes after self.shoppingList, initWitharray, initWithObject, etc.

#import "UIViewController.h"

@interface ViewController : UIViewController

@property (strong, nonatomic) NSArray *shoppingList;

@property (strong, nonatomic) NSString *shoppingCart;

#import "ViewController.h"

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    // Add your code below!
    self.shoppingList = [shoppingList initWithArray: @"toothpaste", @"bread", @"eggs"];


Note the code pasted in is just ONE of many many attempts...

2 Answers

Chris Shaw
Chris Shaw
26,662 Points

Hi Erick,

To create a new NSArray instance we need to create it via alloc which creates a new instance in memory, then we need to use the initWithObjects method to add 3 objects to it, the other thing to note is you always need nil as the last value as it defines the end of the array in memory.

self.shoppingList = [[NSArray alloc] initWithObjects:@"toothpaste", @"bread", @"eggs", nil];

Happy coding!

Oh crap. I remember using that exact syntax in one of my attempts, but in none of them did I use 'nil'. Ugh.

Thank you very much for help!