Challenge - Name of company shows up as a hexadecimal

Objective-C Programming (2nd Edition) 18. Your First Class
1

Hello!

I have a rather small but annoying problem. I think I completed the challenge the way you were supposed to but I also wanted to add the name of the company when printing out the stock price etc. in my for loop. I tried doing this by using the ‘@’-token (%@) but when it gets logged to the console it shows up as a hexadecimal number. If anyone could help me with this problem I would be very thankful!

BNRStockHolding.h

[code]#import <Foundation/Foundation.h>

@interface BNRStockHolding : NSObject

{
float _purchaseSharePrice;
float _currentSharePrice;
int _numberOfShares;
}

  • (float)purchaseSharePrice;

  • (void)setPurchaseSharePrice:(float)p;

  • (float)currentSharePrice;

  • (void)setCurrentSharePrice:(float)c;

  • (int)numberOfShares;

  • (void)setNumberOfShares:(int)n;

  • (float)costInDollars;

  • (float)valueInDollars;

@end[/code]

BNRStockHolding.m

[code]#import “BNRStockHolding.h”

@implementation BNRStockHolding

  • (float)purchaseSharePrice
    {
    return _purchaseSharePrice;
    }

  • (void)setPurchaseSharePrice:(float)p
    {
    _purchaseSharePrice = p;
    }

  • (float)currentSharePrice
    {
    return _currentSharePrice;
    }

  • (void)setCurrentSharePrice:(float)c
    {
    _currentSharePrice = c;
    }

  • (int)numberOfShares
    {
    return _numberOfShares;
    }

  • (void)setNumberOfShares:(int)n
    {
    _numberOfShares = n;
    }

  • (float)costInDollars
    {
    return [self purchaseSharePrice] * [self numberOfShares];
    }

  • (float)valueInDollars
    {
    return [self currentSharePrice] * [self numberOfShares];
    }

@end
[/code]

main.m

[code]#import <Foundation/Foundation.h>
#import “BNRStockHolding.h”

int main(int argc, const char * argv) {
@autoreleasepool {

	BNRStockHolding *apple = [[BNRStockHolding alloc] init];
	
	[apple setPurchaseSharePrice:421.54];
	[apple setCurrentSharePrice:411.32];
	[apple setNumberOfShares:21];
	
	BNRStockHolding *google = [[BNRStockHolding alloc] init];
	
	[google setPurchaseSharePrice:234.56];
	[google setCurrentSharePrice:132.76];
	[google setNumberOfShares:20];
	
	BNRStockHolding *yahoo = [[BNRStockHolding alloc] init];
	
	[yahoo setPurchaseSharePrice:231.45];
	[yahoo setCurrentSharePrice:542.34];
	[yahoo setNumberOfShares:21];
	
	NSArray *companyStocks = [[NSArray alloc] initWithObjects:apple, google, yahoo, nil];
	
	int i = 0;
	
	for (BNRStockHolding *s in companyStocks) {
		NSLog(@"The company %@'s stock currently has a purchaseprice of $%.2f and have a current share price of $%.2f. You have %d shares in it, and the stock costs $%.2f and it's valued at $%.2f", s, [s purchaseSharePrice], [s currentSharePrice], [s numberOfShares], [s costInDollars], [s valueInDollars]);
			  i++;
	}
			  NSLog(@"You have stock(s) from %d comapnies", i);
	
return 0;
}

}
[/code]

The output:

The output in bold is the “problem”.

Thanks in advance!

2

To be able to print instances of BNRStockHolding by using the ‘%@’ directive in NSLog’s format string,
add the description method to BNRStockHolding class:

- (NSString *)description
{
   NSString * str = [NSString stringWithFormat:@"...", ...];
   return str;
}

“…” means not all shown.

3

Thank you for your answer, but I am afraid I don’t really understand what you mean; How would it work? I declared the method in the .h-file but I’m not sure about the implementation. What kind of message is the “stringWith:” and what would it do? I couldn’t find it as a sendable message. Also, how would this look when you use it in the main.m? I can’t really wrap my head around it. Thank you for your time.

EDT: I solved it! I found this (https://mobiarch.wordpress.com/2013/09/09/writing-a-custom-property-getter-and-setter-in-objective-c/) article which gave me some inspiration :wink: I interpreted what ibex10 wrote above as if the whole NSString-thing only were supposed to be declared in a method (and maybe it’s possible to do that as well), but I thought about how it would work if the NSString had getter- and setter-methods and if that maybe could work, so I declared the following in the .h-file and implemented it in the .m-file, just as all the other functions have been declared and implemented in this chapter:

BNRStockHolding.h

[code]#import <Foundation/Foundation.h>

@interface BNRStockHolding : NSObject

{
float _purchaseSharePrice;
float _currentSharePrice;
int _numberOfShares;
NSString *_name;
}

[…]

  • (NSString *)name;
  • (void)setName:(NSString *)m;
    […]

@end
[/code]

BNRStockHolding.m

[code]#import “BNRStockHolding.h”

@implementation BNRStockHolding

[…]

  • (NSString *)name
    {
    return _name;
    }

  • (void)setName:(NSString *)m
    {
    _name = m;
    }

@end[/code]

I don’t know if what I wrote above is what you were thinking of ibex10, but if you have another solution I would be very glad to learn it!:slight_smile:

4

Oops. That should be:

@implementation BNRStockHolding
...
- (NSString *)description
{
   NSString * str = [NSString stringWithFormat:@"...", ...];
   return str;
}
...
@end

“…” means not all shown.

To see what stringWithFormat: does, read the NSString Class Reference.

5

Oh thanks! That makes a lot of more sense! There’s still a few things that I don’t understand about it though:
I read that the stringWithFormat:-message can take variables/objects/etc. much like NSLog (like this: NSLog(@“Hello %@”, name);, where name is a string), but I don’t understand how this can be used in the main.m to store the name of different things/companies. For instance, my project includes three different companies, which each are a different instance of BNRStockHolding; Wouldn’t the description-method need to have a setter-method so that you can give it a different name for every instance?

6

Use the following example as a guide.

main.m

//  main.m

#import "FooBar.h"

int main (int argc, const char * argv[]) {
    
    Foo * foo = [Foo new];
    FooBar * fooBar = [FooBar new];
    
    NSLog (@"%@", foo);
    NSLog (@"%@", fooBar);
    
    return 0;
}

FooBar.h

// FooBar.h

#import <Foundation/Foundation.h>

@interface Foo : NSObject

@end

@interface FooBar : Foo

@end

FooBar.m

//  FooBar.m

#import "FooBar.h"

@implementation Foo
@end

@implementation FooBar

- (NSString *)description
{
    NSString * str = [NSString stringWithFormat:@"%s, and I live at %p.", "I am a FooBar", self];
    return str;
}

@end

[Become a competent programmer: pretty-function.org]

7

That was exactly what I needed, thank you so much for your help!