Question

In Stephen Kochan’s Objective-C book (I have the 3rd Edition), one init function returns Fraction * and one returns id:

-(Fraction *) initWith: (int) n: (int) d {
    self = [super init];
    if (self)
        [self setTo: n over: d];

    return self;
}

-(id) init {
    return [self initWith: 0 over: 0];
}

(it is on page 198 to 199 of the book). Why is that, and does it matter if both return Fraction * or both return id (or have init return Fraction * and initWith return id)? What are the side effects of doing so, if any?

Answer 1

Init methods typically return the id type because they don’t necessarily return an object of the class they belong to.

For instance, -[NSMutableArray init] actually returns a NSCFMutableArray object.