Big Nerd Ranch Objective C Chapter 17 Challenge - Defining Classes

Question

I'm having trouble working with classes. I have to create "StockHolding" objects that are subclasses of NSObject. I create instance variables and methods. Then I create 3 iterations of the stockholdings complete with names and prices, and I load them into a mutable array. I am having difficulty fast-enumerating through the objects within the array and printing the properties (prices) of each. Problem is I am getting an error when trying to enumerate through objects and print the properties. I have tried a few different ways of solving the problem with no luck. Any ideas? I also noticed currentStock is not printing a name, but a pointer location instead. Perhaps these problems are related. Thanks in advance.

'Header'

#import <Foundation/Foundation.h>

@interface StockHolding : NSObject
{
    float fPurchaseSharePrice; 
    float fCurrentSharePrice; 
    int iNumberOfShares;
}

@property float fPurchaseSharePrice;
@property float fCurrentSharePrice;
@property int iNumberOfShares;

-(float) fCostInDollars; //fPurchaseSharePrice * fNumberOfShares
-(float) fValueInDollars; //fCurrentSharePrice * fNumberOfShares

@end

'Implementation'

#import "StockHolding.h"

@implementation StockHolding

@synthesize fCurrentSharePrice, fPurchaseSharePrice, iNumberOfShares;

-(float)fCostInDollars; //fPurchaseSharePrice * iNumberOfShares
{    
    return (fPurchaseSharePrice * iNumberOfShares);
}

-(float)fValueInDollars; //fCurrentSharePrice * iNumberOfShares
{
    return (fCurrentSharePrice * iNumberOfShares);
}

@end

'Main'

 int main(int argc, const char * argv[])
{

@autoreleasepool {
    StockHolding *Apple = [[StockHolding alloc] init];
    [Apple setFPurchaseSharePrice:225];
    [Apple setFCurrentSharePrice:300];
    [Apple setINumberOfShares:50];

    StockHolding *Cisco = [[StockHolding alloc] init];
    [Cisco setFPurchaseSharePrice:100];
    [Cisco setFCurrentSharePrice:50];
    [Cisco setINumberOfShares:75];

    StockHolding *WalMart = [[StockHolding alloc] init];
    [WalMart setFPurchaseSharePrice:75];
    [WalMart setFCurrentSharePrice:150];
    [WalMart setINumberOfShares:75];

    NSMutableArray *Portfolio = [NSArray arrayWithObjects: Apple, Cisco, WalMart, nil];

    for (NSObject *currentStock in Portfolio){   
        NSLog(@"Purchase Price: %@", currentStock );
        NSLog(@"Details: %f", [currentStock FPurchaseSharePrice]);  //  <---Error is on this line.  It says "No visible @interface for NSObject declares the selector fPurchaseSharePrice"
    }

}
return 0;
}

capitolization is important. Also instead of `for(NSObject *` try `for(StockHolding *` if your object is of the right class type you will get the autocompletion. that is actually the point of subclassing object is to go to the common super as opposed to going directly to NSObject which is every classes superclass — The Lazy Coder, Aug 27 '12 at 21:30
check out the response mark gave as it presents the same scenario in an answer. — The Lazy Coder, Aug 27 '12 at 21:34

score 2 · Answer 1 · answered Aug 27 '12 at 21:18

2

Instead do this for your for loop

for (StockHolding *currentStock in Portfolio){   
    NSLog(@"Purchase Price: %@", currentStock );
    NSLog(@"Details: %f", [currentStock fPurchaseSharePrice]);  //  <---Error is on this line.  It says "No visible @interface for NSObject declares the selector fPurchaseSharePrice"
}

answered Aug 27 '12 at 21:18

Mark

2,666
3
25
29

1

I endorse this response. As it presents the correct object superclass in the for loop and therefore has all the correct method and property accessors. – The Lazy Coder Aug 27 '12 at 21:32

score 0 · Answer 2 · answered Aug 27 '12 at 21:17

In your NSLog: FPurchaseSharePrice should be fPurchaseSharePrice.

Additionally, if you override -(NSString *)description, printing the object will yield that string, as opposed to the pointer for that object that you're currently seeing.

- (NSString *)description
{
    return [NSString stringWithFormat:@"StockHolding: %.2f, %.2f", self.fCostInDollars, self.fValueInDollars];
}

Yields:

Purchase Price: StockHolding: 11250.00, 15000.00

Rather than:

Purchase Price: <StockHolding: 0x7fe438c0a480>

Finally, rather than casting to NSObject in your for loop, you can do:

for (StockHolding *currentStock in Portfolio)

And the may not respond error will go away.

score 0 · Answer 3 · answered Aug 27 '12 at 21:18

Well, like it says: you don't have a method with that name. Method names are case-sensitive in Objective-C, and you declared the property (and corresponding accessor) as fPurchaseSharePrice. You want to use this:

NSLog(@"Details: %f", [currentStock fPurchaseSharePrice]);

Big Nerd Ranch Objective C Chapter 17 Challenge - Defining Classes

3 Answers3