Programming in Objective-C, Sixth Edition

Operations on Fractions

Let’s continue to work with the Fraction class. First, you write a method that enables you to add one fraction to another. You name the method add:, and you have it take a fraction as an argument. Here’s the declaration for the new method:

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

Note the declaration for the argument f:

(Fraction *) f

This says that the argument to the add: method is a reference to an object from the Fraction class. The asterisk is necessary, so the following declaration is not correct:

(Fraction) f

You will be passing one fraction as an argument to your add: method, and you’ll have the method add it to the receiver of the message; the following message expression adds the Fraction bFraction to the Fraction aFraction ...