Cool. Thank you that was sort of my thought. Then went and watched the WWDC
video and went into a bit of a panic.
Scott
On Apr 12, 2012, at 11:18 AM, Ken Thomases wrote:
> On Apr 12, 2012, at 12:04 PM, Scott Andrew wrote:
>
>> I have a question about retain cycles with ARC and blocks.
>>
>> I have the following code:
>>
>> __weak MyViewController* controller = self;
>>
>> [UIView animateWithDuration:.25 animations:^{
>> controller.alpha = 0;
>> }
>> completion:^(BOOL finsihed) {
>>
>> [controller showState];
>> }];
>>
>>
>>
>> -(void) showState {
>> self.textView.text = self.stateText;
>> }
>>
>> I have a question about what happens when I use self in showState. DId i
>> just cause a reference counting issue where I now have an extra retain on
>> self and it's not going to be cleaned up?
>
> No. The compiler looks at the code _in the block_ to know what the block
> should retain. It doesn't (for this purpose) look inside the -showState
> method. It can't even reliably know for sure that the call to -showState in
> the block refers to that implementation of -showState. For example, this
> code could all be called from a superclass which overrides -showState.
>
>> The WWDC video say to use weak pointers to self in the block otherwise there
>> could be retain cycle issues. This is an example. The utility functions are
>> actually quite larger and called from multiple places. I'm not creating the
>> strong refrence via a variable because these blocks won't be called if self
>> doesn't exist.
>
> For this case, you don't even have to worry about referencing self in the
> blocks directly. You don't need to use the weak copy, controller. First,
> the object is not itself retaining the blocks. So, if the blocks retain
> self, that's still not a retain cycle. Second, the blocks will be disposed
> of when the animation completes. So any reference they hold on self is
> released when that happens.
>
> Regards,
> Ken
>
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