Can an object instance release itself? - ios

Question

I need to create some objects that will be waiting for some event. When the waited event is triggered, the object makes some things, and then has no longer any reason to live.
I don't want to have to maintain a list of created objects, so I'd like to do something like this :
main() {
Waiter* myWaiter1 = [[Waiter alloc] initAndWaitForEvent:xxxxxxxxxx];
Waiter* myWaiter2 = [[Waiter alloc] initAndWaitForEvent:xxxxxxxxxx];
Waiter* myWaiter3 = [[Waiter alloc] initAndWaitForEvent:xxxxxxxxxx];
Waiter* myWaiter4 = [[Waiter alloc] initAndWaitForEvent:xxxxxxxxxx];
....
/* myWaiterx are retained */
/* I don't release them */
}
Waiter
- (void) catchSomeEvent:(...*)theEvent {
// do what is expected
[self release]; // Release self
/* the release is there */
}
Will this work, and work fine ?

Answer 1

I find it better when there’s somebody to take care of the waiters, but your code is fine. Objects can do this, there is no technical obstacle that would prevent it. Some classes from the standard library already do something similar, for example UIAlertView.
I don’t think that the static analyzer will like your current API, though. It will probably complain about leaks; it would be better to tweak the interface a bit.
#interface Waiter : NSObject {}
- (id) init;
- (void) startWaitingForEvent: (id) event;
#end
#implementation Waiter
- (void) startWaitingForEvent: (id) event
{
[self retain];
…
}
- (void) eventReceived
{
…
[self release];
}
#end
Then the memory management in user code looks better:
- (void) dispatchWaiters {
Waiter w1 = [[Waiter alloc] init];
[w1 startWaitingForEvent:…];
[w1 release];
}

Answer 2

An object can not suicide. It can either be killed by you(the code you sent to kill it), or by the professional killer NSAutoreleasePool. If you own it, you have to kill it.
Warning: If it doesn't die on time, the population will increase and will mess up the memory.
;-)

Answer 3

On some occasions [self release]; is used, for example for initializers (to force variables that a required in some way), an example:
SomeClass.m:
- (id)initWithString:(NSString *)string
{
self = [super init];
if (self)
{
if (string == nil)
{
[self release];
return nil;
}
// if required values are provided, we can continue ...
}
return self;
}
- (id)init
{
return [self initWithString:nil];
}
A caller would call this like:
- (void)testInitializer
{
SomeClass *classInstance1 = [[SomeClass alloc] initWithString:#"bla"];
// classInstance1 != nil, any method calls will work as expected ...
SomeClass *classInstance2 = [[SomeClass alloc] initWithString:nil];
// classInstance2 == nil, will ignore any method calls (fail silently)
SomeClass *classInstance3 = [[SomeClass alloc] init];
// classInstance3 == nil, will ignore any method calls (fail silently)
}
I would guess since the above works fine, you shouldn't have any issues, though it doesn't seem a very clean solution.