Getting Wrong Result

[Pandop]

When i run the program everything works fine except for when pressing = when getting the result

i believe this part of code is whats giving me the wrong result but its what was showed in the book
so for example if i do 1/2 + 1/2 i get = 37/202

Code: (Objective-C)

- (void) processDigit: (int) digit
{
    currentNumber = currentNumber * 10 + digit;
    
    [displayString appendString: [NSString stringWithFormat: @"%i" , digit]];
    display.text = displayString;
}

Calculator.h

Code: (Objective-C)

#import <UIKit/UIKit.h>
#import "Fraction.h"

@interface Calculator : NSObject

@property (strong, nonatomic) Fraction *operand1, *operand2, *accumulator;

-(Fraction *) performOperation: (char) op;
-(void) clear;

@end

calculator.m

Code: (Objective-C)

#import "Calculator.h"

@implementation Calculator

@synthesize operand1, operand2, accumulator;

-(id) init
{
    self = [super init];
    
    if(self)
    {
        operand1 = [[Fraction alloc] init];
        operand2 = [[Fraction alloc] init];
        accumulator = [[Fraction alloc] init];
    }
    
    return self;
}

-(void) clear
{
    accumulator.numerator = 0;
    accumulator.denominator = 0;
}

-(Fraction *) performOperation:(char)op
{
    Fraction *result;
    
    switch (op) {
        case '+':
            result = [operand1 add: operand2];
            break;
            
        case '-':
            result = [operand1 subtract: operand2];
            break;
            
        case '*':
            result = [operand1 multiply: operand2];
            break;
            
        case '/':
            result = [operand1 divide: operand2];
            break;
    }
    
    accumulator.numerator = result.numerator;
    accumulator.denominator = result.denominator;
    
    return accumulator;
}

@end

Fraction.h

Code: (Objective-C)

#import <UIKit/UIKit.h>

@interface Fraction : NSObject

@property int numerator, denominator;

-(void) print;
-(void) setTo: (int) n over: (int) d;
-(Fraction *) add: (Fraction *) f;
-(Fraction *) subtract: (Fraction *) f;
-(Fraction *) multiply: (Fraction *) f;
-(Fraction *) divide: (Fraction *) f;
-(void)       reduce;
-(double)     convertToNum;
-(NSString *) convertToString;

@end

Code: (Objective-C)

#import "Fraction.h"

@implementation Fraction

@synthesize numerator, denominator;

-(void) setTo:(int)n over:(int)d
{
    numerator = n;
    denominator = d;
}

-(void) print
{
    NSLog(@"%i/%i", numerator, denominator);
}

-(double) convertToNum
{
    if (denominator != 0)
    {
        return (double) numerator/denominator;
    }
    else
    {
        return NAN;
    }
}

-(NSString *) convertToString
{
    if (numerator == denominator)
    {
        if (numerator == 0)
        {
            return @"0";
        }
        
        else
        {
            return @"1";
        }
    }
    
    else if (denominator == 1)
    {
        return [NSString stringWithFormat: @"%i", numerator];
    }
    
    else
    {
        return [NSString stringWithFormat: @"%i/%i", numerator, denominator];
    }
}


// add a fraction to the receiver

-(Fraction *) add: (Fraction *) f
{
    // To add two fractions
    // a/b + c/d = ((a*d) + (b*c)) / (b*d)
    
    //result will store the result of the addition
    Fraction *result = [[Fraction alloc] init];
    
    result.numerator = numerator * f.denominator + denominator * f.numerator;
    
    result.denominator = denominator * f.denominator;
    
    [result reduce];
    return result;
}

-(Fraction *) subtract:(Fraction *)f
{
    // a/b - c/d = ((a*d) - (b*c)) / (b*d)
    
    Fraction *result = [[Fraction alloc] init];
    
    result.numerator = numerator * f.denominator - denominator * f.numerator;
    
    result.denominator = denominator * f.denominator;
    
    [result reduce];
    return result;
}

-(Fraction *) multiply:(Fraction *)f
{
    Fraction *result = [[Fraction alloc] init];
    
    result.numerator = numerator * f.numerator;
    
    result.denominator = denominator * f.denominator;
    
    [result reduce];
    return result;
}

-(Fraction *) divide:(Fraction *)f
{
    Fraction *result = [[Fraction alloc] init];
    
    result.numerator = numerator * f.denominator;
    
    result.denominator = denominator * f.numerator;
    
    [result reduce];
    return result;
}

-(void) reduce
{
    int u = numerator;
    int v = denominator;
    int temp;
    
    if (u == 0)
    {
        return;
    }
    
    else if (u < 0)
    {
        u = -u;
    }
    
    while (v != 0)
    {
        temp = u % v;
        u = v;
        v = temp;
    }
    
    numerator /= u;
    denominator /= u;
}
@end

ViewController.h

Code: (Objective-C)

#import <UIKit/UIKit.h>
#import "Calculator.h"

@interface ViewController : UIViewController

@property (strong, nonatomic) IBOutlet UILabel *display;

-(void) processDigit: (int) digit;
-(void) processOp: (char) theOp;
-(void) storeFracPart;

// Numeric Keys

-(IBAction) clickDigit: (UIButton *)sender;

//Arithmetic Operation keys

-(IBAction) clickPlus;
-(IBAction) clickMinus;
-(IBAction) clickMultiply;
-(IBAction) clickDivide;

//Misc. Keys

-(IBAction) clickOver;
-(IBAction) clickEquals;
-(IBAction) clickClear;
-(IBAction) clickConvert;
@end

ViewController.m

Code: (Objective-C)

#import "ViewController.h"

@implementation ViewController

{
    char                op;
    int                 currentNumber;
    BOOL                firstOperand, isNumerator;
    Calculator          *myCalculator;
    NSMutableString     *displayString;
}

@synthesize display;

- (void)viewDidLoad
{
    firstOperand = YES;
    isNumerator = YES;
    displayString = [NSMutableString stringWithCapacity: 40];
    myCalculator = [[Calculator alloc] init];
    
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.
}

- (void) processDigit: (int) digit
{
    currentNumber = currentNumber * 10 + digit;
    
    [displayString appendString: [NSString stringWithFormat: @"%i" , digit]];
    display.text = displayString;
}

- (void) clickDigit: (UIButton *) sender
{
    int digit = sender.tag;
    
    [self processDigit: digit];
}

- (void) processOp: (char) theOp
{
    NSString *opStr;
    
    op = theOp;
    
    switch (theOp) {
        case '+':
            opStr = @" + ";
            break;
        
        case '-':
            opStr = @" - ";
            break;
        
        case '*':
            opStr = @" x ";
            break;
        
        case '/':
            opStr = @" / ";
            break;
    }
    
    [self storeFracPart];
    firstOperand = NO;
    isNumerator = YES;
    
    [displayString appendString: opStr];
    display.text = displayString;
    
}

- (void) storeFracPart
{
    if (firstOperand) {
        if (isNumerator) {
            myCalculator.operand1.numerator = currentNumber;
            myCalculator.operand1.denominator = 1; // e.g. 3 * 4/5 =
        }
        else
            myCalculator.operand1.denominator = currentNumber;
    }
    else if (isNumerator) {
        myCalculator.operand2.numerator = currentNumber;
        myCalculator.operand2.denominator = 1; // e.g. 3/2 * 4 =
    }
    else {
        myCalculator.operand2.denominator = currentNumber;
        firstOperand = 0;
    }
}

- (IBAction) clickOver
{
    [self storeFracPart];
    isNumerator = NO;
    [displayString appendString: @"/"];
    display.text = displayString;
}

// Arithmetic Operation keys

-(IBAction) clickPlus
{
    [self processOp:'+'];
}

-(IBAction) clickMinus
{
    [self processOp: '-'];
}

-(IBAction) clickMultiply
{
    [self processOp: '*'];
}

-(IBAction) clickDivide
{
    [self processOp: '/'];
}

-(IBAction) clickEquals
{
    if(firstOperand == NO)
    {
        [self storeFracPart];
        [myCalculator performOperation: op];
        
        [displayString appendString:@" = "];
        [displayString appendString:[myCalculator.accumulator convertToString]];
        display.text = displayString;
        
        currentNumber = 0;
        isNumerator = YES;
        firstOperand = YES;
        [displayString setString: @""];
    }
}

-(IBAction) clickClear
{
    isNumerator = YES;
    firstOperand = YES;
    currentNumber = 0;
    [myCalculator clear];
    
    [displayString setString: @""];
    display.text = displayString;
}

-(IBAction) clickConvert
{
    display.text = [NSString stringWithFormat: @"%f", [myCalculator.accumulator convertToNum]];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

@end