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    <p>If an application has an increasing memory footprint on a known stable state for example named A after going into and coming back from state B which should have no persistent affect on state A and there is no memory leaks this problem called (as much as I know) the lingering memory.</p> <p>Checklist to be sure if you have lingering memory problem:</p> <ul> <li>App has no memory leaks, or no memory leaks on non-system code when profiled by Instruments.</li> <li>State A and State B are individually stable states, like in state-machine. State B has no permanent affect on State A, or it's memory. State A could be a gateway, a menu to another states like State B or State C. But Child states has no or limited info about state A and makes no change about State A.</li> <li>On loop state changes starts and ends with root state for example A->B->A, A->C->A, A->B->C->A; you encounter increasing memory usage on State A. Memory usage on other child states are not important.</li> </ul> <p>To spot and solve this problem profile your app with instruments. But instead of monitoring leaks, you should monitor allocations and total memory. Every time your app gets to State A, including start, take a memory snapshot. (There is a button for that :D) After snapshot go to State B, State C and use your application as it suppose to. After coming back to root state, in this example State A, take another snapshot. Instruments will show you memory allocations and difference delta in total memory between snapshots. It will also give information about for which object the memory had allocated and when if possible. If it was your code you probably will see the type of class and allocation point. Instruments can not help you about when the object should have been released but when you got the lingering object or memory, figuring out the deallocation point should be much easier.</p> <p>BUT! Do not forget: OS and Framework codes could have leaks and lingering memory problems like every OS. If you are sure that it is not your code leaking or lingering in the memory the everything is fine. That was the case in my app and it got approved(App: Tusudoku). System function often use additional memory if there is available, but they immediately release it when received memory warning. Although devices has limited memory, it is a waste if still not used, and using memory does not make memory chip to use measurably increased electrical current. Using memory to the limits for performance and immediately releasing it when someone definitely needs it, is best possible practice. These cache memories does not tend to be grove over time linearly but you should force memory warning every time app gets to root state, in this example State A. So this way you will be sure any cache memory allocated by system or frameworks will be deallocated, then you take the snapshot.</p> <p>Most of the apps on the App Store® has memory leaks and other memory problems. The question is how this affect user. Non-linear lingering memory with rapidly dropping acceleration on increase velocity generally won't be a reason for rejection. Calculated the memory usage as 15MB for a perfect working app but if it worked, no problem, say that it will reach 20MB limit max ever and you are good to go. So you later fix your memory problems. Bu if your application has a linear or worse increasing memory usage and can not release that memories when needed, that will be a critical problem.</p> <p>For more information about memory usage please consider reading official documentation and watching WWDC videos(That's where I learned all about memory fixes using Instruments).</p>
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