iOS -- initWith methods under arc

Question

In the old days, we were trained to write init methods like this:

Foo.h:

-(id) initWithInteger: (NSInteger) someNumber;

Foo.m:

-(id) initWithInteger: (NSInteger) someNumber {
    if ((self = [super init])) { 
       doSomeStuff;
    }
    return self;
 }

But those id casts are now no-nos. So how should these methods now look?

EDIT: This is for a library. So there is no telling what the calling code might look like.

Answer 1

Why do you say returning id is a no-no? The ARC specification says

init methods must be instance methods and must return an Objective-C pointer type. Additionally, a program is ill-formed if it declares or contains a call to an init method whose return type is neither id nor a pointer to a super-class or sub-class of the declaring class (if the method was declared on a class) or the static receiver type of the call (if it was declared on a protocol).

Moreover, remember that using ARC is a per-file decision, i.e. the code compiled with ARC can be used with the code without ARC, and vice versa. In the case of the header file for a library, you should prepare it so that it can be used on both, but preparing it for non-ARC case should suffice.

Answer 2

Here's what I do now:

-(id) initWithInteger: (NSInteger) someNumber {
    self = [super init];
    if (self) { 
       doSomeStuff;
    }
    return self;
}

It makes the warnings go away and it's logically equivalent, although not quite as elegant.

Duh, I feel like a fool now and didn't read the question to understand it. But I found this link that points to something that might help. Specifically it states, in Section 5:

init methods must be instance methods and must return an Objective-C pointer type. Additionally, a program is ill-formed if it declares or contains a call to an init method whose return type is neither id nor a pointer to a super-class or sub-class of the declaring class (if the method was declared on a class) or the static receiver type of the call (if it was declared on a protocol).

Based on that, it looks like you don't have to do anything, which makes sense. Not even Apple is that cruel to its developers. Are you getting compiler errors? I haven't yet jumped to Lion so ARC is not on my radar yet.