Question

When referencing a weak ivar inside of a block in Objective-C when ARC is enabled, does the runtime implicitly retain the object to which the ivar belongs? For example:

- (void) foo {
    void (^block)() = ^{
        [_weakIvar doSomethingAwesomeButNotTooAwesome]; // Is self retained here?
    }
    block();
}

While we’re at it, how about a weak property in the same scenario?

- (void) foo {
    void (^block)() = ^{
        [self.weakProperty doSomethingAwesomeReallyAwesomeDudeYeah];
    }
    block();
}

Answer 1

_weakIvar really means self->_weakIvar under the hood which means that what is (automatically) retained is self. Same thing applies when doing self.weakProperty.

In your particular example, the block is not copied (and used right away) so nothing is retained at all but if you do (for example):

- (void) foo {
    void (^block)() = ^{
        [_weakIvar doSomethingAwesomeButNotTooAwesome];
    }
    dispatch_async(queue, block); // here, block is copied and so self is retained
}