How to return an instance of a class?

I'm getting the following error:

"warning: conflicting types for '-(Fraction *) add: (Fraction *) f;"

with the line:

-(Fraction *) add: (Fraction *) f;

Here is my header code:

  // Define the Fraction class

    @interface Fraction : NSObject {
        int numerator;
        int denominator;
    }
    @property int numerator, denominator;

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

    @end

Here is my .m code:
#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 1.0;
}
-(void) setTo: (int) n over: (int) d
{
    numerator = n;
    denominator = d;
}


-(void) reduce 
{
 开发者_运维问答   int u = numerator;
    int v = denominator;

    int temp;

    while (v != 0) {
        temp = u % v;
        u = v;
        v = temp;
    }

    numerator /= u;
    denominator /= u;

}

-(Fraction *) add: (Fraction *) f;
{
    // To add two fractions:
    // a/b + c/d = ((a*d) + (b*c)) / (b *d)
    // multiply the denominators
    // then mulitply each numerator by the OPPOSITE
    // denominator

    // result will store the result of the addition
    Fraction *result = [[Fraction alloc] init];
    int     resultNum, resultDenom;

    resultNum = numerator * f.denominator + denominator * f.numerator;
    resultDenom = denominator * f.denominator;

    [result setTo: resultNum over: resultDenom];
    NSLog(@"%i, %i", resultNum, resultDenom);
    [result reduce]; // reduces the numerator and denominator
    // as both are instance (classwide) variables
    NSLog(@"%i is the result", result);
    return result;
}
@end

You have two different implementations of add:. One is:

-(void) add: (Fraction *) f;

inside the interface (.h file). The other is in the implementation (.m file)

-(Fraction *) add: (Fraction *) f;

You will need to change the header to read this latter declaration, so that it returns a Fraction pointer, not void.

That's because in your header file, you've declared the return type to be void:

-(void) add: (Fraction *) f;

Yet, in your implementation, you implement the method returning a Fraction pointer:

-(Fraction *) add: (Fraction *)

Also, you have a semicolon in your implementation, maybe just a copy-paste error?

You are declaring the add method to return void in your interface, but your implementation returns Fraction *