On 26 Jan 2012, at 3:51 PM, Jan E. Schotsman wrote:
> This code is given in the "Transitioning to ARC Release Notes" as an example
> of accomodating blocks in an ARC environment:
>
> __block MyViewController *myController = [[MyViewController alloc] init…];
There is a MyViewController object named myController
> myController.completionHandler = ^(NSInteger result)
It retains a void(^)(NSInteger) block (or a copy thereof.
> {
> [myController dismissViewControllerAnimated:YES completion:nil];
The block refers to myController, so the block automatically retains it.
myController <-> block is a cycle
> myController = nil;
Now the block no longer refers to myController, so myController is released.
> };
When myController is deallocated, it releases the block. No cycle.
>
> Supposedly this avoids a retain cycle. But where is the cycle? At least two
> objects are needed for a cycle. What is the second one?
— F
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