IPhone Development - returning an instance

Question

With code like,
NSString *str;
int x = 3
str = [NSString stringWithFormat:@"%i", x];
How would I go about coding something like that for my own class, where I return an instance? Right now I'm doing this:
Fraction *f = [[Fraction alloc] initWithNumerator:3 andDenominator:5];
[f autorelease];
return f;
and I'd like to do:
return [Fraction fractionWithNumerator:3 andDenominator:5];
Thanks

Answer 1

If I'm understanding your question correctly, you want a class method that will return an autoreleased instance of a Fraction*.
So, change your method from:
- (Fraction *)initWithNumerator:(int)n andDenominator:(int)d;
to something like:
+ (Fraction *)fractionWithNumerator:(int)n andDenominator:(int)d;
and change your:
- (Fraction *)initWithNumerator:(int)n andDenominator:(int)d {
[super init];
if (self) {
[self setNumerator:n andDenominator:d];
return self;
to something like:
+ (Fraction *)fractionWithNumerator:(int)n andDenominator:(int)d {
Fraction* f;
f = [[self alloc] init]);
[f setNumerator:n andDenominator:d];
return [f autorelease];