Parsing through this document on class clusters, NSNumber
implements initWithChar:
in roughly the following manner:
- (id)initWithChar:(char)c
{
[self release];
return [[__NSCharNumber alloc] initWithChar:c];
}
Similarly, you could use this pattern for initializing views from a Nib:
- (id)initWithFrame:(CGRect)frame
{
id realSelf = [[self class] nib] instantiateWithOwner:nil options:nil][0];
realSelf.frame = frame;
[self release];
return realSelf;
}
I'm wondering, does ARC manage the releasing of the unreturned self
in these cases? Is it documented anywhere?
Found the details in the clang documentation.
init
implicitly uses the __attribute__((ns_consumes_self))
attribute, meaning that while self
is defined as __strong id self
, the initial assignment does not perform a retain. This means as soon as self
is reassigned or the function terminates, self
will be released using standard strong rules.
To get an +1 out, there is an implicit __attribute((ns_returns_retained))
which prevents the returned object from being released at the end.
At a high level, ARC plans to release the initial value of self
one extra time by the end of the function, while also retaining the return value, maintaining its +1 output.
It would fall under standard ARC object ownership rules, whereby the "unreturned self
" would end up without any strong references and would therefore be automatically released for you when it falls out of scope.
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