Question

I have a program which runs fine, but I get no print output even though I have a NSLog file in main.m Can you tell me what’s wrong? Thank you.

main.m

#import <Foundation/Foundation.h>
#import "Stockholding.h"

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

  @autoreleasepool {

    StockHolding *stockA;
    StockHolding *stockB;
    StockHolding *stockC;

    [stockA setPurchaseSharePrice:2.40];
    [stockA setCurrentSharePrice:3.12];
    [stockA setNumberOfShares:40];

    [stockB setPurchaseSharePrice:1.50];
    [stockB setCurrentSharePrice:1.41];
    [stockC setNumberOfShares:35];

    [stockC setPurchaseSharePrice:1.10];
    [stockC setCurrentSharePrice:1.20];
    [stockC setNumberOfShares:60];


    NSArray *holdings = [NSArray arrayWithObjects:stockA, stockB, stockC, nil];

    for (StockHolding *n in holdings) {
      // Call the methods
      float cost = [n costInDollars];
      float value = [n valueInDollars];
      NSLog(@"Bought stock for $%.2f, It is now at $%.2f, I have %d shares, They cost me $%.2f, Now they are worth $%.2f", [n purchaseSharePrice], [n currentSharePrice], [n numberOfShares], cost, value);
    }
  }
    return 0;
}

StockHolding.h

#import <Foundation/Foundation.h>

@interface StockHolding : NSObject {
  float purchaseSharePrice;
  float currentSharePrice;
  int numberOfShares;
}

@property float purchaseSharePrice;
@property float currentSharePrice;
@property int numberOfShares;

-(float)costInDollars;
-(float)valueInDollars;

@end

StockHolding.m

#import "StockHolding.h"

@implementation StockHolding

@synthesize purchaseSharePrice, currentSharePrice, numberOfShares;

-(float)costInDollars
{
  return (purchaseSharePrice * numberOfShares);
}

-(float)valueInDollars
{
  return (currentSharePrice * numberOfShares);
}

@end

Answer 1

You haven’t actually created any of those StockHolding objects. Thus, your array is empty, and the loop doesn’t do anything.

StockHolding *stockA;

is just a declaration of a pointer. You need to create the object to which it points; the usual procedure is this:

StockHolding *stockA = [[StockHolding alloc] init];

Since, under ARC, object pointers are initialized to nil (which means “no object”), you are passing nil as all of the arguments to arrayWithObjects:. nil being the sentinel value meaning “there are no more arguments”, the array is created without contents.

With an empty array, for (StockHolding *n in holdings) doesn’t have anything to enumerate over, so none of the code in the body of the loop, including your NSLog(), gets executed.