Question

I’m teaching myself iOS 5 programming through the Stamford University CS193P class, I just started and am on the first project. I want to echo values to the console using NSLog(), and any logs I send to the console from within my controller show up, however any NSLog messages sent from the model class do not. Am I doing something wrong?

From my CalculatorViewController.m file:

- (IBAction)enterPressed
{
    //The Following NSLog() works.
    NSLog(@"Adding number %g to operandStack", [self.display.text doubleValue]);
    [self.brain pushOperand:[self.display.text doubleValue]];
    self.userIsInTheMiddleOfEnteringANumber = NO;
}

From my CalculatorBrain.m file:

-(void)pushOperand:(double)operand
{
    //The Following NSLog() doesn't show up in the console
    NSLog(@"Received number %@ for operandStack", operand);
    NSNumber *operandObject = [NSNumber numberWithDouble:operand];
    [self.operandStack addObject:operandObject];
}

The code isn’t working correctly either, everything compiles and runs just fine, no warnings or errors, but the methods in the model aren’t returning the expected objects, they’re (nil), so I feel like maybe the way the controller is interacting with the model is wrong?

This is how I’m instantiating the CalculatorBrain model BTW:

#import "CalculatorViewController.h"
#import "CalculatorBrain.h"

@interface CalculatorViewController()
@property (nonatomic) BOOL userIsInTheMiddleOfEnteringANumber;
@property (nonatomic, strong) CalculatorBrain *brain;
@end

@implementation CalculatorViewController

@synthesize display = _display;
@synthesize userIsInTheMiddleOfEnteringANumber = _userIsInTheMiddleOfEnteringANumber;
@synthesize brain = _brain;

-(CalculatorBrain *)brian
{
    if (! _brain) _brain = [[CalculatorBrain alloc] init];
    return _brain;
}

Answer 1

There’s a typo in your getter for brain. When you message self.brain, it’s always going to return nil because the mistyped method, brian (where you do your instantiation), isn’t being messaged.

-(CalculatorBrain *)brian
{
    if (! _brain) _brain = [[CalculatorBrain alloc] init];
    return _brain;
}

Also the format specifier for a double is %f. So your NSLog should look like this…

NSLog(@"Received number %f for operandStack", operand);