My Solutions

Objective-C Programming (2nd Edition) 24. Collection Classes
1

Here is my code for both challenges. Any suggestions welcome!

BNRPortfolio.h

#import <Foundation/Foundation.h>
@class BNRStockHolding;

@interface BNRPortfolio : NSObject

@property (nonatomic, copy) NSArray *holdings;

- (NSArray *) mostValuableHoldings;
- (NSArray *) holdingsSortedAlphabetically;
- (float)totalValue;
- (void)addStock:(BNRStockHolding *)s;
- (void)removeStock:(BNRStockHolding *)r;

@end

BNRPortfolio.m

@interface BNRPortfolio ()
{
    NSMutableArray *_holdings;
    NSMutableArray *_mostValuableHoldings;
    NSMutableArray *_holdingsSortedAlphabetically;
}

@end
...
// Most valuable holdings challenge
- (NSArray *)mostValuableHoldings
{
    _mostValuableHoldings = [self.holdings mutableCopy];

    NSSortDescriptor *vid = [NSSortDescriptor sortDescriptorWithKey:@"valueInDollars"
                                                          ascending:NO];
    NSSortDescriptor *nos = [NSSortDescriptor sortDescriptorWithKey:@"nameOfStock"
                                                          ascending:YES];
    [_mostValuableHoldings sortUsingDescriptors:@[vid, nos]];

    NSInteger holdingsCount = [_mostValuableHoldings count];
    while (holdingsCount > 3) {
        [_mostValuableHoldings removeLastObject];
        holdingsCount--;
    }

    return [_mostValuableHoldings copy];
}

// Holdings sorted alphabetically challenge
- (NSArray *)holdingsSortedAlphabetically
{
    _holdingsSortedAlphabetically = [self.holdings mutableCopy];

    NSSortDescriptor *nos = [NSSortDescriptor sortDescriptorWithKey:@"nameOfStock"
                                                          ascending:YES];
    [_holdingsSortedAlphabetically sortUsingDescriptors:@[nos]];

    return [_holdingsSortedAlphabetically copy];

}

Implementations in main.m

...
        // Most valuable 3 holdings
        NSLog(@"\nMost valuable 3 holdings");
        for (BNRStockHolding *stock in stockHoldings.mostValuableHoldings) {
            NSLog(@"Holdings sorted in descending order of value: %@, with a value of %.2f", stock.nameOfStock, stock.valueInDollars);
        }

        // Holdings sorted alphabetically challenge
        NSLog(@"\nHoldings sorted alphabetically");
        for (BNRStockHolding *stock in stockHoldings.holdingsSortedAlphabetically) {
            NSLog(@"%@ stocks cost $%.2f, now worth $%.2f. Value changed by $%.2f.", stock.nameOfStock, stock.costInDollars, stock.valueInDollars, stock.totalLossGain);
        }
...