I can not figure out how to resolve SIGABRT error in Xcode - objective-c

Question

I am working on a basic calculator app, following a tutorial for an iTunes U class. I thought I had worked it out perfectly but when I go to run the application in the simulator, I get an unexpected error. The calculator works by entering the number, pressing the enter button, entering the second number, then the enter button and then the operation. It allows me to append digits to form a multi-digit number, but as soon as I press "enter" it quits out and says "Thread 1: Program received signal: "SIGABRT."" I have double and triple checked my code and cannot seem to find anything wrong, so i thought i would post it all on here and see if you guys can figure it out. Thanks in advance!
CalculatorBrain.h
#import <Foundation/Foundation.h>
#interface CalculatorBrain : NSObject
- (void)pushOperand:(double)operand;
- (double)performOperation:(NSString *)operation;
#end
CalculatorBrain.m
#import "CalculatorBrain.h"
#interface CalculatorBrain()
#property (nonatomic, strong) NSMutableArray *operandStack;
#end
#implementation CalculatorBrain
#synthesize operandStack = _operandStack;
- (NSMutableArray *)operandStack
{
if (!_operandStack) {
_operandStack = [[NSMutableArray alloc] init];
}
return _operandStack;
}
- (void)pushOperand:(double)operand
{
NSNumber *operandObject = [NSNumber numberWithDouble:operand];
[self.operandStack addObject:operandObject];
}
- (double)popOperand
{
NSNumber *operandObject = [self.operandStack lastObject];
if (operandObject) [self.operandStack removeLastObject];
return [operandObject doubleValue];
}
- (double)performOperation:(NSString *)operation
{
double result = 0;
if ([operation isEqualToString:#"+"]){
result = [self popOperand] + [self popOperand];
} else if ([#"*" isEqualToString:operation]) {
result = [self popOperand] * [self popOperand];
} else if ([operation isEqualToString:#"-"]) {
double subtrahend = [self popOperand];
result = [self popOperand] - subtrahend;
} else if ([operation isEqualToString:#"/"]) {
double divisor = [self popOperand];
if (divisor) result = [self popOperand] / divisor;
}
[self pushOperand:result];
return result;
}
#end
CalculatorViewController.h
#import <UIKit/UIKit.h>
#interface CalculatorViewController : UIViewController
#property (weak, nonatomic) IBOutlet UILabel *display;
#end
CalculatorViewController.m
#import "CalculatorViewController.h"
#import "CalculatorBrain.h"
#interface CalculatorViewController()
#property (nonatomic) BOOL userIsInTheMiddleOfEnteringANumber;
#property (nonatomic, strong) CalculatorBrain *brain;
#end
#implementation CalculatorViewController
#synthesize display;
#synthesize userIsInTheMiddleOfEnteringANumber;
#synthesize brain = _brain;
- (CalculatorBrain *)brain
{
if(!_brain) _brain = [[CalculatorBrain alloc] init];
return _brain;
}
- (IBAction)digitPressed:(UIButton *)sender {
NSString *digit = [sender currentTitle];
if (self.userIsInTheMiddleOfEnteringANumber) {
self.display.text = [self.display.text stringByAppendingString:digit];
} else {
self.display.text = digit;
self.userIsInTheMiddleOfEnteringANumber = YES;
}
}
- (IBAction)enterPressed
{
[self.brain pushOperand:[self.display.text doubleValue]];
self.userIsInTheMiddleOfEnteringANumber = NO;
}
- (IBAction)operationPressed:(UIButton *)sender
{
if (self.userIsInTheMiddleOfEnteringANumber) {
[self enterPressed];
}
NSString *operation = [sender currentTitle];
double result = [self.brain performOperation:operation];
self.display.text = [NSString stringWithFormat:#"%g", result];
}
#end

Answer 1

Open CalculatorViewController.xib file in Xcode and right-click the "File's Owner".
Check the appearing pop-up if you have any linked properties listed that are not implemented in the CalculatorViewController.h file (according to the above posted code, the only properties linked from .xib to .h should be a UILabel called "display". Delete all invalid linked properties, if any is available (invalid linked properties would be marked with a yellow warning sign).

Answer 2

Expand your project Executable and right click on it. and click on GetInfo->Argument tag aat end of the window you see plus and minus sign button click on + sighn button and write
Name Value
NSZombieEnabled YES
then after execute your project and whenever crash your application click on run munu-> console you see there why your application crash. please try this may be this will help you.