Question

I’m trying to display in a label on my main screen the size of NSMutableArray when the screen loads 1st time and then every time I hit the Add button, but I get errors such as “Expression result unused”. I tried several options but still no success…
Please advise me with your inputs, thanks! 🙂

int arraySize;
NSMutableArray *arrRaceCars;

- (void)viewDidLoad
   {
[super viewDidLoad];
arrRaceCars = [[NSMutableArray alloc]init];
arraySize = [self numberOfObjectsInArray:arrRaceCars]; // call for a method that should return the number of objects in array

self.lblCarsCount.text = @"%d cars in the race", &arraySize;
}

// ...part of the Add button validation; in case that everything is OK, the code below should add an object to the array and change the display of number of cars in the array in the label

else
{
    self.carType = [segmentedSelectCar titleForSegmentAtIndex:segmentedSelectCar.selectedSegmentIndex];
    self.carName = self.txtCarName.text;
    self.carSpeed = [self.txtCarSpeed.text intValue];

    car* newCar = [[car alloc]initCarWithName:carName carType:carType carMaxSpeed:carSpeed];
    NSLog(@"Car type is: %@, Car name is: %@, Car speed is: %d", self.carType, self.carName, self.carSpeed);

    [arrRaceCars addObject:newCar];

    arraySize = [self numberOfObjectsInArray:arrRaceCars];

    self.lblCarsCount.text = @"%d cars in the race", &arraySize; // this is the problematic line      
    [self alertMessage:@"addNewCar" :@"Your car has been added!" :nil :@"OK" :nil];
}

// this is the method that should return the number of objects within the array 
-(int) numberOfObjectsInArray : (NSMutableArray*) arrayToCheck
  {
     return [arrayToCheck count];
  }

Answer 1

Instead of

self.lblCarsCount.text = @"%d cars in the race", &arraySize; // this is the problematic line      

you should be using:

self.lblCarsCount.text = [NSString stringWithFormat: @"%d cars in the race", [arrRaceCars count]]

The first line of code compiles, but the compiler doesn’t know you want to do a string with a format (the “expression result unused warning”) which is why you should put the explicit “stringWithFormat” method call in there.