Declaration of constructor which allocates and initializes itself in Objective C

Question

Possible Duplicate:
Class methods which create new instances

How would you declare a constructor in objective-c which would allow you to skip the [[class alloc] init] step during a declaration; Instead of saying for example Fraction* somefrac=[[Fraction alloc] init];, just say Fraction* somefrac and the constructor would do the rest.

Answer 1

This would instantiate the object and return it. Following naming conventions you would need to make it an autorelease'd object that gets returned.

+ (id)fraction
{
    return [[[self alloc] init] autorelease];
}

To use it

Fraction *fraction = [Fraction fraction];

this follows the same pattern as the apple provided classes e.g.

NSArray *myArray = [NSArray array];