Fraction class

Fraction.h

//
//  Fraction.h
//  FractionCalculator
//
//  Created by Devon Blandin on 9/15/12.
//  Copyright (c) 2012 Devon Code Shop. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface Fraction : NSObject

@property int numerator;
@property int denominator;

-(Fraction *) add: (Fraction *) f;
-(Fraction *) subtract: (Fraction *) f;
-(Fraction *) multiply: (Fraction *) f;
-(Fraction *) divide: (Fraction *) f;
-(void) print;
-(NSString *) toString;
+(int) gcd: (int) num1:(int) num2;
+(int) lcm: (int) num1:(int) num2;

@end

Fraction.m

//
//  Fraction.m
//  FractionCalculator
//
//  Created by Devon Blandin on 9/15/12.
//  Copyright (c) 2012 Devon Code Shop. All rights reserved.
//

#import "Fraction.h"

@implementation Fraction
@synthesize numerator;
@synthesize denominator;

// instance methods

// adds self to f
-(Fraction *) add:(Fraction *)f
{
    Fraction *result = [[Fraction alloc] init];
    int gcd = [Fraction gcd:denominator :[f denominator]];
    [result setNumerator:((numerator * [f denominator]) + ([f numerator] * denominator)) / gcd];
    [result setDenominator:(denominator * [f denominator]) / gcd];
    
    return result;
}

// subtracts f from self
-(Fraction *) subtract:(Fraction *)f
{
    Fraction *result = [[Fraction alloc] init];
    int gcd = [Fraction gcd:denominator :[f denominator]];
    [result setNumerator:abs((numerator * [f denominator]) - ([f numerator] * denominator)) / gcd];
    [result setDenominator:abs(denominator * [f denominator]) / gcd];
    return result;
}

// multiplies self and f
-(Fraction *) multiply:(Fraction *)f
{
    Fraction *result = [[Fraction alloc] init];
    int gcd = [Fraction gcd:numerator * [f numerator] :denominator * [f denominator]];
    [result setNumerator:(numerator * [f numerator]) / gcd];
    [result setDenominator:(denominator * [f denominator]) / gcd];
    return result;
}

// divides self and f
-(Fraction *) divide:(Fraction *)f
{
    Fraction *result = [[Fraction alloc] init];
    Fraction *f_flipped = [[Fraction alloc] init];
    [f_flipped setNumerator:[f denominator]];
    [f_flipped setDenominator:[f numerator]];
    int gcd = [Fraction gcd:numerator * [f_flipped numerator] :denominator * [f_flipped denominator]];
    [result setNumerator:(numerator * [f_flipped numerator]) / gcd];
    [result setDenominator:(denominator * [f_flipped denominator]) / gcd];
    return result;
}

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

-(NSString *) toString
{
    NSString *string = [[NSString alloc] init];
    string = [NSString stringWithFormat:@"%i/%i", numerator, denominator];
    return string;
}

// class methods
+(int) gcd:(int)num1:(int)num2
{
    if (num2 == 0) {
        return num1;
    }
    return [Fraction gcd:num2:num1 % num2];
}

+(int) lcm:(int)num1:(int)num2
{
    return abs((num1 * num2) / [Fraction gcd:num1:num2]);
}

@end