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POWhat might be a strategy to detect a retain cycle in an object hierarchy programmatically?
 

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  1. POWhat might be a strategy to detect a retain cycle in an object hierarchy programmatically?
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    <p>I'm writing an ARC-enabled framework which creates a hierarchy of objects, not unlike Cocoa's view hierarchy. Each controller object can have several subcontrollers. Controllers may have references to each other, which poses the potential risk of creating a retain cycle.</p> <p><strong>I know how to avoid retain cycles. I want to know if there's a way for me to detect programmatically that a retain cycle exists and prevents an object from deallocating?</strong></p> <p>At some point, the existing root controller will be replaced by a new root controller. Since I'm using ARC I can't use retainCount to check the existing controller's retain count. Which is not to be trusted anyway from what I've read.</p> <p>I have a test setup where the root controller has two sub controllers, and each of them has a strong reference to the other. In that case the root controller does not run dealloc, neither do the other two controllers when the root controller is replaced with a new controller. As expected. I was thinking that given this scenario, there should be some way for me to determine whether that root controller did actually deallocate or not.</p> <p><strong>Possible Solution:</strong> I did assign the to-be-replaced root controller to a zeroing weak property on a global object shortly before replacing the controller. Then I have setup a timer so that after a fraction of a second I check if the property is nil or not. If it's nil, the controller did deallocate. If it's not nil, it probably indicates a memory leak likely to have been caused by a retain cycle somewhere in the hierarchy. In that case I print a log statement for as long as the replaced controller is not nil to get the developer's attention.</p> <p>This works, but are there any alternative (better) solutions? Or possible caveats with this solution? </p> <p>Specifically, how much time can pass before the object deallocates - is this guaranteed to be instantaneous or can deallocation be delayed and if so, for how long?</p>
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