A std::tr1::shared_ptr for Objective C++ on iPhone?

Question

I am mostly a C++ developer, recently I am writing iPhone applications.

The memory management on iPhone is OK to me, due to resource limitation, it's encouraged to use reference counters rather than deep copy.

One annoying thing is I have to manage the reference counters by myself: alloc means counter = 1; retain means counter++, release means counter--

I wish to write a shared_ptr like class for Cocoa Touch, so I rarely have to manually manipulate the reference counters by myself.

I doubt if there's any existing code for that, and I'd like to hear some advices, today is the 5th day since I started to learn objective c

Thanks.

Answer 1

As long as you learn the memory management rules first, there is no real problem with shared_ptr - it can help you in C++ contexts but doesn't let the ownership questions magically disappear.
shared_ptr supports a custom deallocator so the following:

@interface A : NSObject
- (void)f;
@end

@implementation A
- (void)dealloc { NSLog(@"bye"); [super dealloc]; }
- (void)f { NSLog(@"moo"); }
@end

void my_dealloc(id p) {
    [p release];
}

// ...
{
    shared_ptr<A> p([[A alloc] init], my_dealloc);
    [p.get() f];
}

... outputs:

moo
bye

... as expected.

If you want you can hide the deallocator from the user using a helper function, e.g.:

template<class T> shared_ptr<T> make_objc_ptr(T* t) {
    return shared_ptr<T>(t, my_dealloc);
}

shared_ptr<A> p = make_objc_ptr<A>([[A alloc] init]);