Initializing a subclass in objective c

Question

I think that this may be impossible, but what I was trying to do write an static initializer in my super class "load" that will initialize even my subclasses.

+ (id) load
{
    Class c = [self class];
    NSString *cString = NSStringFromClass([self class]);
    NSLog(@"%@",cString);

    id a = [[c alloc] init];
    [a autorelease];
    return a;
}

The result of [self class] here is the superclass, but I want to initialize the class itself (in this case it will always be the subclass). Maybe this is just a terrible programming idea though.

Is there any particular reason why you need to initialize the subclass from the superclass? Both classes are initialized before any instance of either class is created or any static method is called. — Francisco Silva, Jul 29 '12 at 21:18
Tell us what you are trying to achieve and we may be able to suggest a better way of going about it. As it stands, I have no idea what you are trying to accomplish and therefore can't help! — Aidan Steele, Jul 29 '12 at 23:30
I'm with @FranciscoSilva on this one, this doesn't really make any sense. If you need an instance of your subclass, then initialize with your subclass. The super should not know anything about its subclasses. — sosborn, Jul 30 '12 at 00:41
lets say I had a class a with certain actions to be run on initialization, and it retains itself and will release itself when it is done. so class b inherits from class a, so each time I want to use class b or c or d, etc I must type [[[b alloc] init] release], which to me is a bit unsightly and what it does is not so evident. I would like to replace [[[b alloc] init] release] with [b load], but I would like to define load in a, otherwise it is a waste of time to copy and paste load into b,c,d (inheriting from a). — user1122069, Jul 31 '12 at 00:26

score 0 · Accepted Answer · answered Jul 31 '12 at 08:33

I must type [[[b alloc] init] release], which to me is a bit unsightly and what it does is not so evident.

I disagree. It is very evident what this code is doing. It is allocating class B (classes should be capitalized by the way), initializing it, and then releasing it.

[b load]

On the other hand, this tells me nothing other than the fact that b is loading. What is loading? Does it alloc and init?

I would like to define load in a, otherwise it is a waste of time to copy and paste load into b,c,d (inheriting from a)

This is unsightly, and what is does is not so evident. Also, classes really shouldn't know anything about their subclasses.

IMHO, your solution is not a very good one. The way to do it would be for the superclass to have a load method (I would prefer a designated initializer with a more descriptive name) that has all common functionality in it. Then, in your subclasses, override your load mthod to call the super implementatation, then add whatever code you need to for that particular subclass.

Based off your answer, it could be done to implement a subclass method that will return its class. I actually am already using such a pattern. Load is obvious to me and as it does not include aloof or new, I know that I do not own the object. — user1122069, Aug 01 '12 at 10:24

Initializing a subclass in objective c

1 Answers1