My first Objective-C program :)

Fraction.h

//
//  Fraction.h
//

#import <Foundation/Foundation.h>

@interface Fraction : NSObject

@property int numerator, denominator;

-(void)   print;
-(void)   setTo: (int) n over: (int) d;
-(void)   add: (Fraction *) f;
-(double) convertToNum;

@end

Fraction.m

//
//  Fraction.m
//

#import "Fraction.h"

@implementation Fraction

@synthesize numerator, denominator;

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

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

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

-(void) add: (Fraction *) f {
  // To add two fractions:
  // a/b + c/d = ((a*d) + (b*c)) / (b*d)
  numerator = numerator * f.denominator + denominator * f.numerator;
  denominator = denominator * f.denominator;
}

@end

main.m

// New program separating the files of the Fraction program.

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

int main(int argc, const char * argv[]) {

  @autoreleasepool {
      
    Fraction *aFraction = [[Fraction alloc] init];
    Fraction *bFraction = [[Fraction alloc] init];
    
    // Set two fractions to 1/4 and 1/2, and add them together
    [aFraction setTo: 1 over: 4];
    [bFraction setTo: 1 over: 2];
    
    // Display the results
    [aFraction print];
    NSLog(@"+");
    
    [bFraction print];
    NSLog(@"=");
    
    [aFraction add: bFraction];
    [aFraction print];
    
  }
  
  return 0;

}