Adding and removing objects from NSMutableArray

Question

I am implementing a shopping cart project on an iPad.

I have a class "productItem"

#import <Foundation/Foundation.h>

@interface ProductItem : NSObject

+(instancetype)createProductId:(NSString *)aId description:(NSString *)aDesc price:(int)aPrice;
@property(nonatomic, copy)NSString *productId;
@property(nonatomic, copy)NSString *description;
@property(nonatomic)int price;

@end

A class "CartItem"

@interface CartItem : NSObject

@property(nonatomic,weak)ProductItem *prodItem; @property(nonatomic)int quantity;

+(instancetype)createProdItem:(posProductItem *)aProdItem quantity:(int)aQuantity;

@end

I have another class "ProductStore". This class has 2 NSMUtableAray that stores productItems and cartItems:

@property(nonatomic)NSMutableArray *productItems;
@property(nonatomic)NSMutableArray *cartItems;

I implemented 2 ViewControllers, productSearchViewController and cartViewController. The cartViewController basically displays the elements in cartItems.

The functionalities of productSearchViewController are describe below:

productSearchViewController

• products are displayed in UICollectionView. ProductItems retrieved from the web service are populated into ProductStore NSMutableArray "productItems"

• Product Items can be added into "cartItems".

[CartItem createProdItem:aProdItem quantity:1]; // here aProdItem is ProductItem *

• User can search for product in UISearchBar. I implemented (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString*)searchText to query the web service for data. For each search, I will clear NSMutableArray "productItems" and re-populate it with the data from web service

Because I clear UIMutableArray "productItems", the productItem in NSMutableArray "cartItems" gets deleted too. The cartItem elements are still there but the productItem in each cartItem element are empty: Product id, description and price are empty.

How should i go about solving this problem? should I copy ProductItem object into CartItems when a product is added into shopping cart?

Answer 1

The prodItem is set to nil because you have declared it as a weak property in CartItem in the following line:

@property(nonatomic,weak)ProductItem *prodItem;

You should use a strong property if you need to use it in the CartItem class even though it is removed from the productItems array.

@property(nonatomic,strong)ProductItem *prodItem; 

Although this should solve your problem, it does not actually make much sense to clear the productItems but keep the cartItems.